How to find percent of discount

find the diference first:

42-36 = 6

and the what percent is the diffrence:

6/42 = 0.1428571428571429

multiply by 100 to find the percent sign:

0.1428571428571429*100 = 14.28571428571429%

How to find percent of discount

regular price: $42

Sale price: $36

$\begin{array}{rcll} $36 &=& $42 \cdot ( 100\ \% - x ) \qquad & | \qquad : $42\\ \frac{$36} {$42} &=& 100\ \% - x \\ \frac{36} {42} &=& 100\ \% - x \qquad & | \qquad +x\\ x + \frac{36} {42} &=& 100\ \% \qquad & | \qquad - \frac{36} {42}\\ x &=& 100\ \% - \frac{36} {42} \qquad & | \qquad 100\ \% = 1\\ x &=& 1 - \frac{36} {42} \\ x &=& 1 - \frac{18} {21} \\ x &=& \frac{21 -18} {21} \\ x &=& \frac{3} {21} \\ x &=& \frac{1} {7} \\ x &=& 0.14285714286\\ \mathbf{ x } & \mathbf{=} & \mathbf{ 14.285714286 \ \% } \end{array}$

The discount is 14.29 %