Isabella buys a digital camera and pays $7.20 in sales tax. The tax rate is 6%. What is the original cost of the camera?

The original cost of the camera is $120.

Explanation:
6%=6/100=0.06. This means to find 6% tax on a sale, we multiply the amount of the sale by 0.06; this gives us 0.06x, since we don't know the cost of the camera.

We know the amount of tax is $7.20, so we have the equation 0.06x=7.20.

Divide both sides by 0.06:
0.06x/0.06 = 7.20/0.06
x=120.