First, work out the difference (decrease) between the two numbers you are comparing(which is 15 in this case) . Next, divide the decrease by the original number and multiply the answer by 100.(15/40=0.375 times 100=37.5) If the answer is a negative number, this is a percentage increase
I think the answer would be 37.5% decrease. The boots are $15 less than before so you set 15 over 40 equals x over 100. Cross multiply 40 by x and 15 by 100 to get 40x=1,500. You then divide 1,500 by 40 to get x=37.5 which is your percent decrease. I hope this helped :)
