# How do you define a variable and write an expression for each phrase: the sum of eighteen and b?

Jun 24, 2016

$18 + b$

#### Explanation:

You will need to define a variable when a question refers to "the number of people on a bus", or "the price of a packet of apples", or "a certain number."

In this case the variable is clearly $b$.

The main operation is addition - indicated by the the word "sum".

So what is being added? 18 and the variable $b$.

An expression is merely a statement, while an equation has an equal sign and not asked for on this case.
The expression is $18 + b$