Side XZ corresponds to side AC, the ratio is 18:12.
To find the scale factor, divide 18 by 12.
18 ÷ 12 = 1.5
Multiply the length of side BC by 1.5 and it should equal the length of side YX, 15. This is how you know 1.5 is the scale factor.
10 × 1.5 = 15
Divide 12, the length of XY, by 1.5 to find the length of AB.
12 ÷ 1.5 = 8.
Answer:
Side AB's length is 8.
Hope this helps :)