Answer:
Surface area of the rectangular prism= 
Step-by-step explanation:
Given Dimensions of the rectangular prism are:

Surface Area of a rectangular prism=

=
The surface area of the rectangular prism is 
Answer:
the missing number is 84
Step-by-step explanation:
Let the missing number be represented by N. Then we have ...
7*3 = N*3/(4*3)
Canceling common factors on the right, we have ...
7*3 = N/4
Multiplying by 4 gives ...
4*7*3 = N = 84
The missing number is 84.