We are given
The student council earned $1.25 for every cup of hot chocolate it sold
and $0.75 for every cup of apple cider it sold
total number of cup is 375
we have equation as


The above equation is of total cost equation
We can see that first term is 1.25x
and we have
The student council earned $1.25 for every cup of hot chocolate
so, to find total cost of hot chocolate , we multiplied 1.25 with x
that's why
x must be the number of cups of hot chocolate sold
Hence,
option-C........Answer