What gives us the answer 30?

(a)  

What gives us 16?

(a)  

What gives 24?

(a)  

What gives 64?

(a)  

7*4

(a)  

2*4

(a)  

8*8

(a)  

6*7

(a)  

8*4

(a)  

9*5

(a)  

6*8

(a)  

3*7

(a)  

7*9

(a)