Question 1020249
Let's say the price starts at X.
{{{P=X}}}
During the 15% increase,
{{{P=(1+15/100)X=1.15X}}}
During the unknown decrease,
{{{P=(1+Y/100)(1.15X)}}} "Y is the percentage decrease you're looking for"
Make that new price equal to the original price, X.
{{{(1+Y/100)(1.15)X=X}}}
You can divide X out of both sides.
Now solve for Y.
{{{1.15+(1.15Y)/100=1}}}
Subtract 1.15 from both sides
{{{(1.15)Y/100=-0.15}}}
Multiply both sides by 100 and divide both sides by 1.15.
{{{Y=-15/1.15}}}
{{{Y=-13.04}}}
About a 13% decrease.