Let us consider that the cost price of the washing machine is ₹100.

And here given that the loss is 20%.

Thus, Selling price = Cost price $-$ Loss

= 100  $-$ 20

= ₹80

Using the unitary method:

If the selling price is Rs. 80, then the cost price = Rs.100

Thus, if the selling price is Rs.13,500.

Therefore, the cost price = (100/80)$\times$13,500

= ₹16,875

The cost price of the washing machine = ₹16,875