Tamara J. answered 03/15/13
Math Tutoring - Algebra and Calculus (all levels)
Let 'x' represent the cost before tax.
If the tax on something that costs x dollars is 6%, then the amount of tax on x is:
(6%/100%)x = (0.06)x
Since the total cost after tax is $106, then
cost before tax + cost of tax = 106
That is,
x + 0.06x = 106
Combining like terms, we arrive at the following:
1.06x = 106
Divide both sides of this equation by 1.06 to solve for x:
1.06x/1.06 = 106/1.06
x = 100
Thus, the cost before tax is $100.
You can check this be finding the cost of a 6% tax on something that cost $100, doing so by the following:
100 · (6%/100%) = 100 · 0.06 = 6
So a tax of 6% on $100 is $6, which means that the total cost is the cost of the object before tax plus the tax amount. That is,
$100 + $6 = $106