What is the answer for 10(x-7)=y

Any is very appreciated! (picture is provided below)not sure how to do this at all won't lie

Saline iv fluid bags cost $64.20 for 24, 1000 ml bags from one supplier. a new supplier sells 500 ml bags for $2 each. the hospital uses about 10,000, 1000 ml bags each month. nurses report that about half of the bags are more than half full when they are discarded. if you are going to use only one supplier, which size bag provides the best deal, and how much will you save each month? compare the cost of the new supplier to the current one.

What is r i 4.5+10r=-6.5 with work pls