In the following inequation solving
var('x_0 x_1')
s1=solve(x_1 - 2*x_0 <= 20, x_0)
show(s1)
whatever be the variable x0 or x1 the result obtains is a function of x1. So I try to substitute for solve_ineq()
and then have an error. I need a result in the form x1≤20+2∗x0.