I believe by the first equation they are referring two a representation of the total amount of money made up by the two types of coins. I found this to be 0.05x + 0.10y = 3.50
In my work I solved for the amount of each coin- I assume this is what the final step of your problem entails. If you need any help understanding/ I misinterpreted something please feel free to comment and ask :)
#5c coins or x= 36
#10c coins or y= 17
