We know:
You currently make $13.50 an hour. You've earned a 15% pay raise. You want to find out your previous rate of pay per hour.
Steps:
1.) Convert 15% to a decimal, which equals 0.15
2.) Multiply your current earnings with the percentage in decimal form (0.15)
$13.50 (current pay per hour) x 0.15 (percentage in decimal form) = $2.025 (difference between your previous wage and your current wage)
3.) Subtract the difference of your previous wage and current wage with your current earnings
$13.50 (current pay per hour) - $2.025 (difference between previous and current wage) = $11.475 (previous pay per hour)
4.) Since this is talking about wage, rounding is not applicable. In other cases, your number would be rounded off to $11.48, however you can't add what you don't have, so you would have to round down.
You were previously making $11.47 an hour.