Writing and Evaluating Algebraic Expressions

An algebraic expression is a mathematical phrase that can contain numbers, variables, and operation symbols (like +, -, *, /). For example, $$3x + 5$$ is an algebraic expression.

A variable is a letter or symbol used to represent an unknown number. For example, in the expression $$x + 2$$ , $$x$$ is the variable.

The expression for '9 less than j' is $$j - 9$$ .

The expression for the total cost of tickets for a group of people is $$25t$$ , where $$t$$ is the number of people.

This situation is represented by the expression $$s + 40$$ , where $$s$$ is the amount of money she had before.

An algebraic expression contains variables and numbers (e.g., $$2x + 3$$ ), while a numerical expression contains only numbers and operation symbols (e.g., $$5 + 3$$ ).

To evaluate an algebraic expression means to substitute the values of the variables and perform the operations to find a numerical result.

The expression is $$x + 10$$ .

The expression is $$4y$$ .

The expression is $$15 - z$$ .