Answer:
Step-by-step explanation:
Given that Lindsay is 5 years younger than Mark.
Seven years ago, the sum of their ages was 31.
Let l be Lindsay's age and let m be Mark's age.
From the given Lindsay is 5 years younger than Mark.
We can write it as
l=m-5
From given "Seven years ago, the sum of their ages was 31".
It can be written as
( l - 7 ) + (m- 7) = 31