Method 1
[tex]\begin{array}{ccc}60&-&15\%\\x&-&100\%\end{array}\ \ \ \ |cross\ multiply\\\\15x=60\cdot100\\15x=6000\ \ \ \ \ |divide\ both\ sides\ by\ 15\\\boxed{x=400}[/tex]
Method 2
[tex]\begin{array}{cccc}15\%&-&60&|divide\ both\ sides\ by\ 3\\\\5\%&-&20&|multiply\ both\ sides\ by\ 20\\\\100\%&-&400\end{array}[/tex]
Method 3
[tex]p\%=\dfrac{p}{100}\\\\15\%=\dfrac{15}{100}=0.15\\\\0.15x=60\ \ \ \ |divide\ both\ sides\ by\ 0.15\\x=400[/tex]
