The formula you should use is Area = 1/2bh, in other words, area equals half times base times height. Now, substitute everything in, the equation should now be 221.16 = 1/2*b*29.1. This simplifies into 221.16 = 14.55b, now divide 14.55 on both sides, which leaves us to 15.2 = b. However, don't forget the units, which the answer (length of base) should be 15.2 in.^2.
For each question we must apply the Pythagorean theorem and clear the value of x.
question 5
x = root (14 ^ 2 + 16 ^ 2)
x = root (452)
x = 2raiz (113)
question 6
x = root (8 ^ 2 + 15 ^ 2)
x = 17
question 7
x = root (12 ^ 2 + 12 ^ 2)
x = root (2 * (12 ^ 2))
x = 12raiz (2)
question 8
x = root (18 ^ 2 - 9 ^ 2)
x = root (243)
x = 9raiz (3)