An aquarium holding African cichlids is 4 inches higher than it is wide. Its length is 30 inches, and its volume is 4200 cubic inches. What is the length and width?

H = w + 4;

V = h * w * l;

Then, 4200 = (w + 4) * w * 30;

4200 : 30 = (w + 4) * w;

140 = (w + 4) * w;

w^2 + 4w - 140 = 0;

For ax^2 + bx + c = 0, the value of x is given by:;

In our case, a = 1; b = 4; c = - 140

Roots are - 14 and 10;

The correct answer is w = 10inches because w > 0;

Finally, h = 14 inches.