Answer:
x = 16.8
Step-by-step explanation:
We can use proportions and the triangle angle bisector theorem to solve this problem
20 30
------- = ----------
28-x x
Using cross products
20x = 30(28-x)
Distribute
20x =840 - 30x
Add 30x to each side
20x+30x = 840-30x+30x
50x = 840
Divide each side by 50x
50x/50 = 840/50
x =16.8
