Question

Solve by elimination:
$12x+15y=-18$
$18x-7y=-86$

Answer 1

Given equations

$12x+15y=-\mathrm{18.....}\left(1\right)$

$18x-7y=-\mathrm{86.......}\left(2\right)$

Multiplying (1) by $7$ and (2) by $15$ ,we get

$84x+105y=-\mathrm{126.....}\left(3\right)$
$+$ $270x-105y=-\mathrm{1290.....}\left(4\right)$

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$84x+270x=-126-1290$

$354x=-1416$

$x=-4$

Putting $x=-4$ in (1), we get

$12(-4)+15y=-18$

$15y=48-18$

$15y=30$

$y=2$