The cost of 4 pens and 4 pencils boxes is Re100. Three times the cost of a pen is Re 15 more than the cost of a pencil box. Form the pair of linear equations for the above situation. Find the cost of a pen and a pencil box.

Let the cost of a pen be Re x and the cost of a pencil box be Re y.

4x + 4y = 100

or x + y = 25 …(i)

and 3x = y + 15

3x-y = 15 …(ii)

On adding Eqs. (i) and (ii), we get

4x = 40

So, x = 10

By substituting x = 10, in Eq. (i) we get

Y = 25-10 = 15

Hence, the cost of a pen and a pencil box are Rs 10 and Rs15, respectively.

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