pair of linear equation in two variables

In this case , forming the equations is the most important step.

Let's assume that a man's one day's work is 1/x(which means that a man can finish his work in x days)

Simly assume that a boy's one day's work will be 1/y.

So 8 men's one day's work will be 8/x and 2 boys' one day's work will be 2/y.

So we have the first equation, 8/x +2/y=1/10(as they take 10 days to finish the work)

Simly

 the next equation can be written as

6/x+8/y=1/14

Assume 1/x=u and 1/y=v

Then the equations become

8u+2v=1/10

and

6u+8v=1/14

Solve using, cross multiplication method.