Your answer is $1.26 You can solve this problem with or without a calculator, and I don't know if you're allowed one or not so I'll show you both ways
Calculator: The easiest way to find percentages of values on the calculator is to use the decimal multipliers, which are just the decimal value of the percentage. For example, 50% would be 0.5, 75% would be 0.75 etc. The decimal value of 15% is 0.15, so you would do 8.40 × 0.15 = 1.26
Non-Calculator: This is a bit longer, but gives you the same answer. To solve without a calculator, you first divide 8.40 by 10 to find 10%, which is 0.84. Now you can divide that by 2 to find 5%, which would be 0.42, and then you add the two values (because 10% + 5% = 15%) to get 1.26
