X: y = 5 : 3 and x + y = 56 work out the value of x - y must show working

X : y = 5 : 3 and x + y = 56
3x=5y and x + y = 56
3x=5y and  x=56-y
3(56-y)=5y and  x=56-y
168-3y=5y and  x=56-y
168=8y and  x=56-y
y=168/8 and  x=56-y
y=21 and  x=56-y
y=21 and x=35

x=35
y=21