I suppose both triangles are similar. The ratio of 2 sides in a triangle is the same ratio of the corresponding 2 sides in the second similar triangle. Which means, AB / AC = LM / LN now we can substitute the given values in 5 / (x + 5) = 10 / (3x + 3) Use the cross method to solve this. 10(x+5) = 5(3x+3) 10x + 50 = 15x + 15 50 - 15 = 15x - 10x 35 = 5x X = 7 Now we know the value of x is calculate the length of AC AC = 7 + 5 Therfore the answer is 12
