C + A + S =1118
4.25C + 9.75A + 5.50S = 8037.50
C + 3A + 2S = 2518
This simultaneous set of linear equations is a nuisance to solve. I will start; you finish.
Eliminate the C from the 3rd by subtracting the the first equation from the third: 2A + S = 1400.
Multiply the 2nd equation by 4: 17C + 39A + 22S = 32150.
Now multiply the first equation by 17 and eliminate the C from the 2nd equation by subtraction.
You will now have 2 simultaneous equations in A and S. Solve the set, then use the values of A and S to find C. Good luck!