let

l = the length of the rectangle, l>0

w = the width of the rectangle, w>0

the length of a rectangle is 3ft less than twice the width

l = 2w - 3

the area of the rectangle is 14ft^2

l*w = 14

plug l = 2w - 3 into the last equation

(2w - 3)w = 14

by solving we find

w = 3.5 ft

click here to see the step by step solution of the system of equations

l = 2*3.5 - 3

l = 4 ft

the dimensions of the rectangle are 3.5 ft and 4 ft.