Number 5 and i don't know how to do it at all

Your givens are A+S=326 and 8A+5S=1972.

A+S=326
  -S      -S
A=326-S

if you substitute this into the other equation that you are given it looks like this
8(326-S)+5S=1972.
After this we use PEMDAS to solve for S
2608-8S+5S=1972
2608-3S=1972
-3S=(-636)
-S=(-212)
S=212
If we know S=212 we can go back and solve the origonal equation for A.
A+212=326
A=114

The answer would be b ! explanation: the formula for sa *surface area * is 2×l×w+2×l×h+2×w×h so in this case l=4w=12h=8so you use the formula to solve it and it give you the answer of 352^cm^2