Answer:
b. 19
Step-by-step explanation:
by similarity between two triangles BFG~BAC
- measure of angle BFG = measure of angle BAC by using corresponding angles in parallelism
- measure of angle BGF = measure of angle BCA by using corresponding angles in parallelism
- the third angle common
- so BF÷FA=BG÷GC
- 63÷21=57÷GC
- therefore GC=19
