how does sympy solve work code example

Example 1: sympy solve equation system

sol = solve((eq1, eq2),(x, y))
sol

Example 2: how to write x in terms of y sympy

def express(a, b, name):
    sym = symbols(name)
    sol = solve(a-sym, b)
    assert len(sol) == 1
    return (sym, sol[0])