This is an equilateral triangle, so all angles are 60 degrees, we can set 8y + 12 equal to 60, and 7x + 4 = 60
To simplify 8y + 12 = 60, subtract 12 from both sides to get 8y = 48, divide both sides by 8 and you have y = 6
To simplify 7x + 4 = 60, subtract 4 from both sides to get 7x = 56, divide both sides by 7 and you have x = 8