Explanation:
there are not many choices to find the similar object. so, all we really have to do is finding the scale factor.
1.
HJG is similar to ABC.
scale factor 1/3.
because 6×1/3 = 2, 12×1/3 = 4
2.
NPM is similar to ABC.
scale factor 2.
because 7×2 = 14, 5×2 = 10
3.
KJML is similar to ABCD.
scale factor 2.
because 8×2 = 16, 6×2 = 12
4.
scale factor 1/2.
10×1/2 = 5
40×1/2 = x
x = 20
5.
scale factor 1/3.
21×1/3 = 7
18×1/3 = x
x = 6
6.
scale factor 5.
3×5 = 15.
6×5 = x
x = 30
I just think you marked the wrong sides with 6, 3 and 15. but it does not matter fit the overall result.