Do 42 divided by 15 then divided 12 by the awnser. And you do 42 divided by 28 and divided that by 12 I think I'm pretty sure
22 quarters= $5.50
10 dimes= $1.00
$5.50 + $1.00 = $6.50
I just did trial and error. I started with 20 quarters and made changes until it worked.
Let's begin by listing out the information given to us:
There are four students: n = 4
Number of students to be selected: r = 2
To calculate the combination of 2 students to be chosen, we use:

Therefore, there 12 possible combinations from these
1. 15/3:3/3
2. 5:1
1. find the same denominator
2. divide by denominator
Step-by-step explanation:
given:
$12.50- the price of the tshirts
40- the tshirts they have sold
$850- the raise they need
solve:
$12.50 × 40 = $500 (the price of tshirts and tshirts they have sold)
$850 - $500 = $350 (the raise they need and the money they have so far from the 40 tshirts they have sold)
$350 ÷ $12.50 = 28 (the money they lack and the price of a tshirt)
answer:
thus, they need to sell 28 more tshirts to have the raise of at least $850
hope this helps, good luck! :)