This is number 8. the second person got number 9
Remark
Many calculators have a key that will do this in one step. Mine is one of them. So let's start with the answer and then we'll do it the long way.
9C3 = 84. You put it into your calculator as 9 2nF nCr 3 =
Solution

3*4*7 = 84 which is what you set out to show.
18+36=54
i tried to do all of these and none of them add up to 54
<u>1</u> : 3
8
Make the whole number a fraction, by putting it over 1.
<u>1</u> : <u>3</u>
8 1
Turn the second fraction upside down and multiply:
<u>1</u> . <u>1</u> = <u>1 </u>
8 3 24
S = 1/24
The $50 off was like a coupon after you brought all your merchandise to the counter, so we have to add it back in to determine the number of shirts.
$400+$50=$450 original price of shirts
Original price ÷ price per shirt= quantity purchased
$450 ÷ $15/shirt= 30 shirts purchased
Allison bought 30 shirts.
Hope this helps! :)