5X+ 12Y=400。

X=4Y

The solution is Y= 12.5 X=50.

2. Let the number of big bowls and small bowls be x and y respectively.

Then 6.5X+4Y=98.

X+Y= 17

X= 12 Y=5。

3. Let the bottom length be X and the top and bottom length be X-5.

(X-5+X)(X-5)/2=(X-5)(X-5)+20

The solution is X= 13.

4. Maximum 2500

The minimum value is 99

5. Set X days later

150-20X = 100- 10X

X=5