Question 440317
You can't find numbers. You now have three unknowns with only two equations.

x+y=45
y=45-x
11x+10y= ? 
11x+10*(45-x)=
11x+450-10x=x+450

11x+10y=x+450
10x+10y=450
x+y=45
You can only solve in terms of x or in terms of y.