here let me take a shot at this one. From my chinese studies. 怎么has a few meanings it can mean how, what, somewhat, however, how could. in the sentence 他愿意怎么办就让他怎么办 you need to look at all the other characters around it especially 就 and 让 就-jiu here means just. 让－rang here means let 办－means handle (as in handling affairs such as getting a visa, passport, taxes etc) 办签证。。handle visa. but it's chinese's generic handling all sorts of things. the chinese english translation would be he willing (how to handle) it just let him (how to handle) it. he is willing to handle it just let him handle it. he is willing to do it just let him do it. it all depends on the situation. chinese is a very contextual language. You need to know the context of the conversation to properly translate it into english. Just the one sentence you gave us is not enough to fully translate its meaning chinese speaking people like to say 怎么办 all the time. in question form it means How do I handle it? How do I solve it? what do i do? it depends on the situation. like saying ... my computer is broken... how do I handle it? usually in english we say my computer is broken.... what do i do?

怎么样/怎样 1.WHAT ABOUT ,HOW ABOUT,HOW Eg . 你怎么样？准备好了吗？ What about you? ready? / how is it going? Are you ready? to ask the things,situation 你怎么样？or 怎么样？身体好些了吗？ How do you feel? Are you ok? To ask the heath states 你觉得怎（么）样？我穿上它好看吗？ What do you think about it?/ How about it?/ What do you say? 你想怎（么）样？ What do you want to do? 2. WELL eg. 怎么样，我对吧？ Well,am I right? NOTE: in somewhere,such as Taiwan,they say 怎样 too much.but usually the use similar with 怎么样 怎么办 HOW TO DO.. 我不知道下一步怎么办。I don’t know how to do next? HOW SHOULD DO? 我该怎么办？ How should I do ? WHAT ABOUT…? 如果下雨了怎么办？ What about it rains? 他愿意怎么办就让他怎么办。Let him do(the thing)what/that he wanna do. here 怎么办 can be a combined verb ,let's take place of it with 哭，写作业，看电视 他愿意哭就让他哭。 他愿意写作业就让他写作业。 他愿意看电视就让他看电视。 Also we can consider 怎么办 as two words,and 怎么 is describe how do it,then we can take place of 办 as 哭，写作业，看电视 他愿意怎么哭就让他怎么哭。Well,he can cry aloud,sob,or mimic crying etc. 他愿意怎么写作业就让他怎么写（作业）。He can write it as a narration,exposition or argumentation;he can sit to write or groveling 他愿意怎么看电视就让他怎么看（电视）。He can sit,lie,stand;he can change the channels as he like maybe.

怎，not used separately,usually togther with 么,to be like these: 怎么，怎么样，怎么办 怎么 has different meanings in different cases 1. Questions: means HOW ,WHAT Eg. 你怎么了？ What’s up? What happened to you? 我怎么才能做到呢？ How could/What should I do to make it? 怎么会这样呢？ How could be like this? 怎么回事？怎么啦？ What’s the story/matter? How come….? 2. in Statements:means SO ,WHATEVER/REGARDLESS,WHAT eg. 这本书不怎么好看!The book looks not so good!(the appraisal somehow is your personal) well 这本书不好看! Means This book not good!(sure,objective) 他今天不怎么高兴！He looks not so happy today! Well 他今天不高兴！ Means He is not happy today! 我怎么也完成不了任务了。 I can’t finish this job whatever I do. 你是怎么想就怎么说。 Just say what you think. 3. in oral chinese,it’s the omission of 怎么样 means WELL eg. 怎么（样），你不喜欢这个礼物？ Well,u don’t like the present?

怎样and怎么样 mean how in English e.g. 我做的饭怎么样（怎么）？ 怎么办 mean how to do, how to deal with. It always used as a phrase in Chinese. And It's usually ended with 啊 or begins with 那 in order to express the mood of being anxious. e.g A: The enemy is coming here with advanced weapon. B: 怎么办？（那怎么办？）(怎么办啊？) 怎么 and 怎 are difficult for me to express.

I saw 这本书不怎么好看 and 他今天不怎么高兴. Why would you use them like that why not just say这本书不好看 and 他今天不高兴 怎么here express the different degrees. -The book is not good. -The book is not very well. The former sentence implies the book is bad nearly. The other one implies the book is not as good as I expect. It can be more relaxed tone that use 怎么. For instance: -我不喜欢他. I am sure I am not like him. -我不怎么喜欢他. I donot like some aspects of him perhaps.