Let width be x
Length would be x + 3
Area = L * W
Make an equation
(x) * (x+3) = 70
x^2 + 3x = 70
x^2 + 3x - 70 = 0
Quadratic formula
(-3 +/- rt 3^2 - 4 * 1 * (-70))/(2 * 1)
x1 = (-3 + 17)/2, x2 = (-3-17)/2
x = 7, x = -10
Dimension cannot be negative
Solution: width = 7
Length = 10