Answer:
16.2
Step-by-step explanation:
The angle internal to the triangle at B is the supplement of the one shown, so is 65°. That is equal to the angle internal to the triangle at D. Since the vertical angles at C are congruent, the two triangles are similar by the AA theorem.
Corresponding sides of similar triangles are proportional, so we can write the proportion shown in the attachment:
BC/FC = DC/AC
BC = FC(DC/AC) = 21.6(7.2/9.6)
BC = 16.2 . . . . matches the first choice
X + y = 10
x - y = 2
add the equations together
2x = 12
x = 6
6 + y = 10
y = 3
8.5x2=17
20.6-17=3.6
3.6-1.37=1.23
1.23-0.75=0.48
0.48/4=0.12
the spokes cost $0.12 each