<h3><em>When you write 55% you are basically writing a shortened version of </em></h3><h3><em>55</em></h3><h3><em>100</em></h3><h3><em /></h3><h3><em>So the amount of increase is </em></h3><h3><em>55</em></h3><h3><em>100</em></h3><h3><em> of </em></h3><h3><em>120</em></h3><h3><em>. The mathematical equivalent of the word 'of' is multiply</em></h3><h3><em /></h3><h3><em>So increase is:</em></h3><h3><em> </em></h3><h3><em>55</em></h3><h3><em>%</em></h3><h3><em> of </em></h3><h3><em>120</em></h3><h3><em> </em></h3><h3><em>→</em></h3><h3><em> </em></h3><h3><em>55</em></h3><h3><em>100</em></h3><h3><em>×</em></h3><h3><em>120</em></h3><h3><em>=</em></h3><h3><em>66</em></h3><h3><em /></h3><h3><em>So the new total is </em></h3><h3><em>120</em></h3><h3><em>+</em></h3><h3><em>66</em></h3><h3><em>=</em></h3><h3><em>186</em></h3>
The "inverse operation" is just a way of saying "what do you do to isolate the variable". In this case, we isolate y, so we have to move all terms to the right side. To do that, we subtract 12 from each side to there will only be "y" on the left side.
