You can put this solution on YOUR website!
Let x = first side of the rectangle (width)
x+7 = second side of the rectangle (length)
x+8 = diagonal of the rectangle (hypotenuse of the right triangle)
This is a quadratic equation, so set it equal to zero!
Factor the left side:
x = 5 or x = -3
Since x is a side of a triangle, it cannot be negative. Therefore reject the x=-3.
If x = 5, then x + 7 = 12, and x + 8 = 13.
The rectangle is 5 by 12 and the diagonal is 13.