Answer:
y=15
Step-by-step explanation:
We know that the angles in a triangle add to 180 degrees
∠ABC+∠BAC+∠ACB=180
We don't know what ∠ACB is, but we know it is on a straight line with another angle (∠ACD). They are supplementary, and must add to 180
∠ACB+ ∠ACD=180
∠ACB+146=180
Subtract 146 from both sides
∠ACB=34
Now, we know ∠ABC is 4y+8, ∠BAC is 5y+3 and∠ACB is 34, so we can substitute them in
∠ABC+∠BAC+∠ACB=180
4y+8+5y+3+34=180
Combine like terms
4y+5y+8+3+34=180
9y+45=180
Subtract 45 from both sides
9y=135
Divide both sides by 9
y=15
