In a sale there is 25%off on all prices an tv costs £90 in the sale. how much was it before the sale?

To work out how much something was before the discount, you have to divide the price (which is £90) by 75 (as this is the percentage that you paid). It's gives you £1.20. Therefore, 1% is £1.20. To find the original cost, which is 100%, you have to multiply it by 100. Multiplying £1.20 by 100 gives you £120. Therefore, the cost of the TV before the 25% reeducation was £120. Hope this helps :)

Since 25% off from sale:
That means sale was = (100 -25)% = 75% of marked price.

Let marked price be = x.
Therefore,  0.75x = 90.
                      x = 90/0.75    Use your calculator.
                       x = 120.
   Marked price before sale = £ 120.