Since we are given the perimeter, we add the lengths of the sides and set the sum equal to the perimeter. Then we solve for x.
3x + 3x - 1 + 4x + 1 = 70
10x = 70
x = 7
Now we pick two sides that can be used as a base and a height to calculate the area. In a right triangle, the legs form a right angle, and can be used as base and height.
base = 3x = 3(7) = 21
height = 3x - 1 = 3(7) - 1 = 21 - 1 = 20
area = base * height/2
area = (21)(20)/2 = 21 * 10 = 210
Answer: 210
