## Elementary Technical Mathematics

We use the addition method: We add the 2 equations: $4x+7y=9$ $12x+21y=12$ Multiply both sides of the first equation by $-3$ to cancel $x$. $-12x-21y=-27$ $\underline{+12x+21y=+12}$ $0=-15$ This is a false statement. Thus, the two equations are parallel. No solution.