mult(g(x),y) -> mult(x,y)
mult(x,g(x)) -> g(x)
mult(x,mult(y,z)) -> mult(x,g(y))
g(g(x)) -> g(x)
f(g(x)) -> g(x)
f(f(x)) -> f(x)
g(f(x)) -> f(x)
mult(f(x),x) -> f(x)
mult(x,f(y)) -> mult(x,y)
g(mult(x,y)) -> f(y)
f(mult(x,y)) -> g(x)
mult(f(x),g(x)) -> x
mult(mult(z,x),y) -> mult(f(x),y)