Use the grid to create a model to solve the percent problem.
21 is 70% of what number?

I don't know what grid you are talking about so I'll just show you a different method.

The question is asking you what number is 21 70% of. 
So you see what 1% is by dividing 21/70= 0.3 
So if 1% is 0.3, and you want to find out what 100% (actual number) is, you just multiply 1%= 0.3 by 100
= 30

Therefore, 21 is 70% of 30.