The price of a stock decreased by in 2001, and then decreased by in 2002. What percent increase in 2003 will restore the price to its value at the beginning of 2001? Express your answer to the nearest hundredth.

Original price x

Price in 2001 0.8*x

Price in 2002 0.8*0.8*x

Price in 2003 f*0.8*0.8*x = x so f = 1/(0.8*0.8) = 1.5625

I'll let you work out the percentage increase from here.