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

The present age of Mark is 25 years.

And present age of Lindsay is  20 years.

Step-by-step explanation:

Let us assume:

The present age of Lindsay = l

The present age of Mark = m

⇒ Age of Lindsay seven years ago =  (l -7) years

and Age of Mark seven years ago =  (m -7) years

According to question:

Lindsay is 5 years younger than Mark    ⇒   l = m  - 5

Seven years ago, the sum of their ages was 31  ⇒  (l-7) + (m -7)  = 31

So, the given set of equation are:

l = m  - 5      (1)

(l-7) + (m -7)  = 31

⇒ ((m - 5) -7) + (m -7)  = 32  (from (1)

or, m -12 + m - 7  = 31

or, 2m = 31 + 19 = 50

⇒ m = 50 / 2  = 25, or m  = 25

Hence,the present age of Mark = 25 years

So,the present age of Lindsay = 25 - 5 = 20 years

translate k to n and reflect across the line containing jk.