A bathing suit is on sale for 40% off. Including 7% sales tax, the final price is $57.78. What was the original cost without tax or discount?
Let x be the original cost of the bathing suit without tax or discount.
After a 40% discount, the price is 0.6x.
With 7% sales tax, the price becomes (0.6x) + 0.07(0.6x) = (0.6x)*(1+0.07) = 0.642x
Given that the final price is $57.78, we have:
0.642x = $57.78
x = $57.78 / 0.642
x = $90
Therefore, the original cost of the bathing suit without tax or discount was $90.