Graham paid $87.45 for a pair of jeans. This amount included a tax of 40%. What was the cost of the jeans before tax?

The final price is the cost plus the tax.

Since we know the tax and a percent, we can write this as

T = C(1+r)

T = what Graham paid = $87.45

C = cost before tax

r = tax rate expressed as a decimal = .40

Plugging in what we know

87.45 = C (1+.4)

87.45 = C(1.4)

Divide both sides by 1.4

C = $62.46