“I am three years younger than my brother, and I am 2 years older than my sister. My mom's age is one less than three times my brother's age. When you add all our ages, you get 87. What are our ages?”

ANSWER:
87 = x+Mom + sister + brother
87 = + (3brother-1) + (x - 2) + (x + 3)
87 = x+ (3*(x+3) - 1) +( x - 2) + (x + 3)
87 = x + 3x + 9 - 1 + x - 2 + x +3
87 = 6x + 9
78 = 6x
13 = x