if x is increased by 30% and then decreased by 30%, the result is what percent of x?
trap answer: result = 100% of x
it is a mistake to add and subtract percent increase and decreases: in particular, a percent increase and percent decrease of the same numerical value do no cancel.
in fact, we have to use multipliers.
result = (1.30)*(0.70)*x = 0.91x
answer = 91% of x