<span><span><span>x+<span>3y</span></span>=12</span>;<span><span><span>−<span>4x</span></span>+<span>3y</span></span>=<span>−3</span></span></span>Step: Solve<span><span>x+<span>3y</span></span>=12</span>for x:<span><span><span>x+<span>3y</span></span>+<span>−<span>3y</span></span></span>=<span>12+<span>−<span>3y</span></span></span></span>(Add -3y to both sides)<span>x=<span><span>−<span>3y</span></span>+12</span></span>Step: Substitute<span><span>−<span>3y</span></span>+12</span>forxin<span><span><span><span>−<span>4x</span></span>+<span>3y</span></span>=<span>−3</span></span>:</span><span><span><span>−<span>4x</span></span>+<span>3y</span></span>=<span>−3</span></span><span><span><span>−<span>4<span>(<span><span>−<span>3y</span></span>+12</span>)</span></span></span>+<span>3y</span></span>=<span>−3</span></span><span><span><span>15y</span>−48</span>=<span>−3</span></span>(Simplify both sides of the equation)<span><span><span><span>15y</span>−48</span>+48</span>=<span><span>−3</span>+48</span></span>(Add 48 to both sides)<span><span>15y</span>=45</span><span><span><span><span><span>15y</span>15</span></span></span>=<span><span><span>4515</span></span></span></span>(Divide both sides by 15)<span>y=3</span>Step: Substitute3foryin<span><span>x=<span><span>−<span>3y</span></span>+12</span></span>:</span><span>x=<span><span>−<span>3y</span></span>+12</span></span><span>x=<span><span><span>(<span>−3</span>)</span><span>(3)</span></span>+12</span></span><span>x=3</span><span>(Simplify both sides of the equation)</span>
