What is an expression in mathematics?
An expression in mathematics is a statement that uses either numbers, variables, or both. For example, the following are all mathematical expressions:
6 - 4
5 × x - 7
4 + 5 (3 - 2)
x + 4 (7 - x)
In order to write an expression from a written mathematical problem, one has to interpret the text. For example, one person weighs 100 pounds and another weighs y pounds; the expression for their combined weights would be 100 + y.