Question 175223
Note that you need to create new expressions using the information in the problem.  "If the length is decreased by 10 in." is equivalent to saying 4x-10 since 4x represents the length.  "and the width is increased by 2 in." is equivalent to saying x+2 since x represents the original width.  Then, using the perimeter formula of P = 2W + 2L, we get that

80 = 2(x+2) + 2(4x-10)
Distributing:
80 = 2x + 4 + 8x - 20
Simplifying:
80 = 10x -16
Add 16 to both sides:
96 = 10x
Divide both sides by 10:
9.6 in = x
Thus the original width was 9.6 in and the original length was 4(9.6) = 38.4 in.