<p>The substitution method changes a pair of simultaneous linear equations into one equation containing only one unknown. First write one unknown as an expression in terms of the other unknown.</p>
<ol class="num-list"><li data-list-item-id="sub-s1" data-list-item-path="sub-s1"><div class="list-item-paragraph">Choose either equation and make one unknown the subject. When possible, choose an unknown whose coefficient is \(1\) or \(-1\).</div></li><li data-list-item-id="sub-s2" data-list-item-path="sub-s2"><div class="list-item-paragraph">Substitute the whole expression into the other equation. Use brackets when the expression is multiplied by a number.</div></li><li data-list-item-id="sub-s3" data-list-item-path="sub-s3"><div class="list-item-paragraph">Solve the resulting linear equation in one unknown.</div></li><li data-list-item-id="sub-s4" data-list-item-path="sub-s4"><div class="list-item-paragraph">Substitute this value into the expression from Step 1 to find the other unknown.</div></li><li data-list-item-id="sub-s5" data-list-item-path="sub-s5"><div class="list-item-paragraph">Check the two values in both original equations. For each equation, \(\text{LHS}=\text{RHS}\).</div></li></ol>
<p>State the solution as the ordered pair \((x,y)\).</p>

The substitution method changes a pair of simultaneous linear equations into one equation containing only one unknown. First write one unknown as an expression in terms of the other unknown.

Choose either equation and make one unknown the subject. When possible, choose an unknown whose coefficient is \(1\) or \(-1\).

Substitute the whole expression into the other equation. Use brackets when the expression is multiplied by a number.

Solve the resulting linear equation in one unknown.

Substitute this value into the expression from Step 1 to find the other unknown.

Check the two values in both original equations. For each equation, \(\text{LHS}=\text{RHS}\).

Substitution Method

Substitution Method