Answer:
16
Explanation:
Area of a triangle = 1/2(b×h)
b or l = x+4
h = x
a = 40
1/2(x+4 × x) = 40
1/2(x+4 × x) = 40x + 4 × x / 2 = 40
4 × x = 4x
4x + x = 5x
5x/2 = 40
cross-multiply
40 × 2 = 5x
40 × 2 = 5x80 = 5x
divide both sides by 5
5x/5 = 80/5
5x/5 = 80/5x = 16