Show that the lines represented by `x(a+3b)+y(2a-b)=5a+b` pass through a fixed point for different values of `a` and `b`.

Explanation

`x(a+3b)+y(2a-b)=5a+b`
`implies a(x+2y-5)+b(3x-y-1)=0`
`implies (x+2y-5)+(b)/(a)(3x-y-1)=0`
Which represents a line passing through the intersection of the lines `x+2y-5=0` and `3x-y-1=0`. Their point of intersection is `(1,2)` which is a fixed point.