Since K is the midpoint of JL, it divides the segment JL into two equal halves. That means ⇒ JK = KL Substitute expressions for the parts ⇒ 7x + 4 = 12x - 21 Now solve the equation: 7x - 7x + 4 = 12x - 7x - 21 4 = 5x - 21 4 + 21 = 5x - 21 + 21 25 = 5x 5 = x Substitute the value into one of the expressions: JK = 7(5) + 4 = 39 JL = JK + KL JL = 39 + 39 = 78
