How to solve could not save earnings setting

Yesterday I tried to apply Adsense for my blog ( https://mathsupporter.blogspot.com/ ) but I can't save it on earnings setting. I tried to find the answer in google and youtube but still can find the solution and also try to ask google and youtube why I have that problem but I get nothing. Today after try many time I found my problem and I can save the earnings setting. So I want to share this experience to all that have problem like me.

1. First, the problem is because I used email to sign up Adsense is difference from email that I used for create blog.

2. Second, the solution is after change email that I used for create blog to the email that I used for sign up Adsense and wait about 6 hours I can save the earning setting.

Problem: 

Do you know how to change admin email in blogger?

Do you know how to sign up Adsense directly from blogger?

Do you know how to make your blog qualify for  Adsense?

If you can't you can comment here, I will try to help you.