you have a bottle of water with a leak. after 2 seconds there is 28 ounces left in the bottle. after 6 seconds there are 20 ounces left in the bottle. how much water was in the bottle initially

Between the 2 second mark and 6 second mark, 4 seconds passed and 8 ounces leaked out.
8 ÷ 4 = 2, the ounces per second leaking. 
Multiply it by 2 to get 4, the amount leaked after 2 seconds. 
Add 4 to 28 to get 32 ounces, the initial amount. 
Hope this helps!