Question

If I should cook food for 7 billion people then how much water should I use​

Answer 1

Let us assume that the amount of water used for 1 million people = x
Then the amount of water used for 7 million people=7*x
=7x

Answer 2

Let us assume that the amount of water used for 1 million people = x

Then the amount of water used for 7 million people=7 × x

=7x