Question

Tim is k years old and Jennifer is 4 years younger than Tim. Find their average age in 3k years' time, in terms of k.

Answer 1

Write both Tim and Jennifer's age in terms of k
Tim = k
Jennifer = k - 4

Now in 3k years
Tim = k + 3k
Jennifer = k - 4 + 3k

Simplify
Tim= 4k
Jennifer = 4k-4

Now to find average
( Tim + Jennifer)/2

Plug in
(4k + 4k-4)/2

(8k-4)/2

Simplify
4k-2

I hope this is what you're looking for!