When finding a discount that has a percentage, we have to multiply the amount of the specific item being discounted and the percentage of the discount. In this case, we have a forty-five dollar headset at a twenty-five percent discount rate. To find the price, multiply the amount of the headset by the percentage of the discount.
$45 * 25%
$11.25
Meaning that the price of the discount will be eleven dollars and twenty five cents.
by deduction, 5 and 7 are prime numbers and 15 is not a multiple of 70, therefore the answer must be 10 as it is a non-prime number and is a factor of 70 (I.e. 10 and 7)