Question

Lisa is 10 centimeters taller than her friend Ian. Ian is 14 centimeters taller than Jim. Every month, their heights increase by 2 centimeters. In 7
months the sum of Ian's and Jim's heights will be 170 centimeters more than Lisa's height. How tall is Ian now?

Answer 1

Let Lisa's height be x, Ian's be y and Jim's be z
x = 10 + y . . . (1)
y = 14 + z . . . (2)
y + 14 + z + 14 = 170 + x + 14
y + z - x = 170 + 14 - 28 = 156 . . . (3)
From (2), z = y - 14 . . . (4)
Putting (1) and (4) into (3) gives,
y + y - 14 - 10 - y = 156
y = 156 + 24 = 180

Therefore, Ian's height is 180 centimeters