You have a certain number of chocolates and you don't know the number of chocolates. If you receive the same number of chocolates from your friend and another friend gives you thrice the number of chocolates, which of the following can represent the total number of chocolates you have?
5x
You can take any variable to represent the number of chocolates you have. Consider 'x' to be the number of chocolates.
Now if you receive the same number of chocolates from your friend, you will now have twice the number of chocolates you had initially.
Since another friend gives you the thrice the number you had, he's giving you '3x' chocolates.
Hence, the total number of chocolates you have now will be '2x+3x=5x'.