28% of what number is 7?

Cross Multiply

= 
28x = 100 · 7
28x = 700
28       28
   x = 25

or you can set it up like this...

28% of what number is 7

1. Change 28% to .28 
     .28 of what number is 7

2. Of means multiply 
     .28 · what number is 7

3. what number is going to be a variable I will use x
     .28 · x is 7

4.  is means equal to 
     .28 · x = 7
     
Finally you can solve the equation

.28 · x = 7

divide both sides by .28
    .28 · x =  7 
    .28         .28
            x = 25