Answer:
Triangle is isosceles, so the angles opposed to equal sides are equal, so you can write down a condition, in this case y=42 (the two equal angles are marked with the line). x is found by difference, since the internal angles sum to 180, and it's the solution to x + 42 + 42 = 180, so 96.
Most of these kind of problems are solved with this system: identify if there are equal angles (ie, they're part of an isosceles triangle, or if they are opposite by a vertex) and write equations based on them
