Question

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

Answer 1

`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`