Answer: 125
Step-by-step explanation:
The sum of all 3 interior angles of a triangle is 180.
18 + (12y + 5) + (4y - 3) = 180
20 + 16y = 180
Subtract 20 from both sides
16y = 160
Divide both sides by 16
y = 10
Now plug y back into equation for angle A
12y + 5
12(10) + 5
120 + 5 = 125
