You were given the final price and must find the original cost to the seller. I like to think of these in terms of perentage problems with the percentage formula. 80 over what amount is equal to 125%?

80/x = 5/4 (multiply each side by x)

80 = 5/4x (Divide each side by 4/5 now to get x alone)

80 (4/5) = x, x = $64 (This is your original price of the item)

Don't forget the final step of $80-$64 = $16 of profit.

medea66 wrote:Please advise....

Its 16. U can also use a formula..

cost price = (100/100 + gain%)* selling price

thus CP = 100/125*80 =64

thus profits is SP- CP

80 -64 = 16.

Hope it helps..

medea66 wrote:Please advise....

there are multiple ways and all above are correct solution. Another is as follows

Final Sale with 25% profit = $80
cost (1.25 ) = $80
cost = $80/1.25 = 80*4/5 = $64

Profit = Final Sale - Cost = $80 - $64 = $16

I did use the percent formula, my problem was that I was trying to find out 25% of 80 instead of 125% of 80. So I guess whenever there are percents involved w/ trying to find original something, the "1" should be added in front of the percent given

When X is increased by 52% you do X*1.52
When X is increased by 2% you do X*1.02

When Y decreases by 20% you do Y*0.8
When Y decreases by 5% you do Y*0.95

Thanks pepeprepa! That helps, I'll add that to my lessons.