Question 148088
Solve the auxiliaries for y first.

y<=24-3x
y<=33/2 -3x/2

Now, if y>=0,
24-3x >=0
33/2 - 3x/2 >=0

Moreover,
if x>=0, 
-3x>=-24
-3x/2>=-33/2

Even further,
x<=8
x<=11

So the maximum of x will be 8. 

Now, 
y<=0 follows from the first condition with restriction x<=8. So the maximum of y will be 0.

Thus,
z=20x + 8y

z=20*11=220

Which is answer (a).