Mr lee bought a washing machine he had to pay an additional 90 which was a 15% sales tax how much did the washing machine cost

Let's assume the initial cost of the washing machine is x.

The sales tax on the washing machine is 15% of x, which is 0.15x.
Mr. Lee had to pay an additional 90, so we can set up the equation:
0.15x = 90
Dividing both sides by 0.15:
x = 90 / 0.15
x = 600
Therefore, the washing machine cost 600.