Answer:
12
Step-by-step explanation:
the shapes are similar which means the sides are proportional, you can set up a ratio using the sides as 10/40 = 3/x
solving that gives you x =12
9 ÷ 3/2 = 6
21 ÷ 7/3 = 9
12/7 ÷ 2/7 = 6
4 2/3 ÷ 7/9 = 6
72/7 ÷ 8/7 = 9
4 1/2 ÷ 1/2 = 9
i dont think I can help I am really sorry
