A trapezoid has a base of length 4, another base of length s, and a height of length s. A square has sides of length s. What is the value of s such that the area of the trapezoid and the area of the square are equal?

The correct answer is: 4

Given, base of trapezoid = 4, s
Height = s
Sides of square = s
Area of square = s*s = s²
Area of trapezoid = ½ * (4+s) * s = (4s + s² )/2= 2s + s² /2

Area of square = Area of trapezoid
s² = 2s + s² /2
s² /2 = 2s
s= 4 units.

Area of the given polygons:
Area of square = s*s = s² 
Area of a trapezoid = ½ x sum of parallel sides x distance between them