In a sale, normal prices are reduced by 10%.
Nathalie bought a pair of shoes in the sale for £54.
What was the original price of the shoes?

You do 54/x = 90%/100. As prices are reduced by 10%, 54 is 90% of the original number. After cross multiplying you get 5400=0.9x. Which turns into 6000. Adding the decimal point back on you get £60.00.

So the original price of the shoes is £60.00.

Checking: all you have to do is take 10% of 60, which is 6 and subtract 6 from 60 to get 54. Thus, 60 is your answer.

Hope this helps!