First solve the second equation to equal x.
x + y = 550
Subtract y from both sides.
x = 550 - y
Put this into the first equation in place of x.
3.75 (550 - y) + 4y = 2160
Multiply everything in the parenthesis by 3.75
2062.5 - 3.75y + 4y = 2160
Combine like terms.
2062.5 + 0.25y = 2160
Subtract 2062.5 from both sides.
0.25y = 97.5
Divide 0.25 on both sides.
y = 390
Put this into the second equation in place of y.
x + 390 = 550
Subtract 390 from both sides.
x = 160
So x = 160 and y = 390
Hope this helps!
