Write and solve an equation to solve the problem. lisa is 4 centimeters taller than her friend ian. ian is 8 centimeters taller than jim. every month, their heights increase by 2 centimeters. in 4 months, the sum of ian's and jim's heights will be 140 centimeters more than lisa's height. how tall is ian now? let h be ian's height today in centimeters.
(h + 8) + + 8 = ( + 8 + 140

ian is __ centimeters tall now.

Let the actual heights of Lisa, Ian and Jim be L, I and J.

i) "Lisa is 4 centimeters taller than her friend Ian." means: L=4+I

ii) "Ian is 8 centimeters taller than Jim." means: I=8+J, thus J=I-8

so the heights of Lisa, Ian and Jim are  4+I, I and I-8, respectively.

Since their heights increase by 2 cm, in 4 months, their heights increase      2 cm*4 = 8 cm.

Thus, after 4 months the heights of Lisa, Ian and Jim become:

4+I +8, I+8 and I-8+8 that is  I + 12, I+8, I.

In 4 months, "the sum of Ian's and Jim's heights will be 140 centimeters more than Lisa's height. " mean:

(I+8)+I=140+(I+12)

2I+8=152+I

I=152-8=144

This solution made use of writing all the ages in terms of Ians current age.