Answer:
BC = 15
Explanation:
Because of parallel lines, AD and BE, triangles ADC and BEC are similar.
In similar triangles, the lengths of corresponding sides are proportional.
AC/BC = DC/EC
We see that AC = AB + BC = 3 + BC
Also, DC = DE + EC = 2 + 10 = 12
(3 + BC)/BC = 12/10
(3 + BC)/BC = 6/5
Cross multiply.
5(3 + BC) = 6BC
15 + 5BC = 6BC
15 = BC
BC = 15