It is given that 4 bottles of water costs $10. Find the unit price per bottle of water, by simply dividing 4 from both the bottle of water as well as the cost:
(4 bottles of water/$10)/(4/4) = (1 bottles of water/(10/4)) = 1 bottles of water/2.5
Each bottle costs $2.50
Check. Multiply the unit price per amount of units bought:
2.50 x 4 = 10
Next, find the unit price for 3 bottles. Multiply the unit price with the amount of bottles bought:
