Let’s assume the cost of a pen and pencil be ₹ a and ₹ b respectively.

Then, forming equations according to the question

…(a)

…(b)

On multiplying equation (a)by and equation (b) by we get

…(c)

…(d)

Now on subtracting equation (c) from equation (d), we get

Putting in equation (a), we find b

Therefore, the cost of one pen and so the cost of one pencil