Answer:
The leghts of AB is 9 because both of the triangles are symmetrical. But also, this is a Equilateral triangle, which means that both of the sides are the same lengths (AB=AC)
It will take him 30 hours
14.
4(5.6) = 4(6.0 - 0.4) = 4(6.0) - 4(0.4) = 22.4
16.
4(6 + 7) = 4(6) + 4(7) = 52
18.
14(10 - 5) = 14(10) - 14(5) = 70