Because the problem stated that "the rancher plans to use 100 feet of fencing", we know that all of the sides of the fence must add up to 100 ft. Using this information, you set up an equation.
100=x+x+(x+4)+(x-3)+5 Then you combine like terms:
100=4x+6 Subtract 6 from both sides:
94=4x Divide both sides by 4:
23.5=x
Therefore, x=23.5 ft.