Which variable would you like to solve for?
Let's try solving for y since you have two of them.
ky - bf = fy/m
kym - bfm = fy --> [ multiply by m ]
kym - fy = bfm --> [ subtract fy on both sides ]
y(km-f) = bfm ---> [ factor out a y ]
y = bfm/(km-f) ---> [ divide by km-f on both sides ]