How many ml is in 2 liters?

Hint:
Liters is the metric unit of volume and ml (milli-liter) is its $ \dfrac{1}{1000} $ th part, or 1,000 ml = 1 liter. Let's say we have an 'x' number of ml in 2 liters. We can convert both of them into the same units by multiplying / dividing with an appropriate multiplier (see Note below).

Complete Step by step Solution:
We know that 1 liter is equal to 1,000 ml.
Multiplying both of them by 2, we get:
⇒ 1 × 2 liters is equal to 1,000 × 2 ml.
⇒ 2 liters is equal to 2,000 ml, which is the required answer.

Note:
Remember that we can add / subtract or multiply / divide both sides of the equation by the same number, without affecting the equality. To find the value of the variable, eliminate the terms so as to have all the terms containing the variable on one side and the constants (numbers) on the side of the equality. Since this is a linear equation, there will be a single value of the variable which satisfies the equation.
Some common prefixes of the metric system and their equivalent mathematical meaning is given below: