You'd need to start by finding what 40% of 280 is. To do this, you turn 40% into a decimal which is .40 . Multiply .40 x 280 which is 112. Then subtract that answer from 280 which is 168 baseball cards. Hope this helped :)
To find the perimeter of a rectangle, we can use this formula:

Where L is the length and W is the width.
We know the perimeter and we know the length and we want to find the width.
Substitute the values back into the formula.
2(35) + 2W = 84
70 + 2W = 84
2W = 14 <-- Subtract both sides by 70
W = 7 <-- Divide both sides by 2
So, width is 7 meters long.
(0.5 liter/bottle) x (6 bottles/pack) = 3 liters/pack
(10 days) x (1.5 liter/day) / (3 liter/pack) = <u>5 packs</u>