Answer:
14
Step-by-step explanation:
Since they are similar triangles, we can use proportions
5 10
------ = -------------
5+7 10+?
5 10
------ = -------------
12 10+?
Using cross products
5( 10+?) = 12*10
Divide each side by 5
10+? = 12*10/5
10+? = 24
Subtract 10 from each side
10+?-10 = 24-10
? = 14
