3y + 5 = -10
3y = -10 - 5 --- Shift 5 to right side of equal which changes it from a positive 5 to a negative 5
3y = -15 --- -10 - 5 = -15
y = -5 --- Since both sides are divisible by 3, we divide them by 3 to simplify the answer. 3y / 3 = y & -15 / 3 = -5