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
