Samuel takes 5 coolers to his basketball game each cooler holds 9 liters of water how many liters of water altogether did he take to the game

Consulting your 4th-grade times tables, you know Samuel took 5*9 = 45 liters of water to the game.

In case you forgot that math fact, you can use a calculator to reproduce it.

In case you forgot that multiplication simplifies repeated addition, you can simply add up the numbers.
.. (9 L) +(9 L) +(9 L) +(9 L) +(9 L) = 45 L