This application solves a system of two linear equations with substitution. It solves the first equation for $y$ and then substitutes $y$ into the second equation. A new equation is then solved for $x$. Two equivalent equations give the identity, so there are infinitely many solutions; in case of a contradictory (inconsistent) system, there are no solutions. You can also observe the geometric counterparts of the solutions.

$a_1$ $a_2$
$b_1$ $b_2$
$c_1$ $c_2$