200-(x- 10)20(x-8)=700
(400-20 times) (x-8)=700
(20-x)(x-8)=35
20x- 160-x? +8x=35
x? -28x+ 195=0
x= 13,x= 15
(2)200-(x- 10)20(x-8)=-20x? +560x-3200=-20(x- 14)? +720
X= 14 is the maximum.