In a sale, all prices are reduced by 40%. Calculate the original price of an article whose sale price is $42.

Think: If prices are reduced by 40%, then the customer is paying 60% of the original cost. This 60% is \$42 and we need to find the original price.
Let x be the original price of the article.
To develop a proportion for solving, say “60% is to 100% as \$42 is to x” and write that in proportion form: \( \frac{\mathrm{60} }{\mathrm{100}} = \frac{\mathrm{42} }{\mathrm{x}}\)
Cross-multiply to get a solvable equation: 60x=4200
Divide both sides by 60 to get 70. The original price was \$70.