Exercise 42 Page 8

Let's begin by reviewing the definition of an algebraic expression. An algebraic expression is a mathematical phrase that consists of both variables and numbers. They can be multiplied, divided, added, or subtracted from each other.

Algebraic Expression	Not an Algebraic Expression
$2 x + 3 y ✓$	$2 + 3 (4) \times$
$8 f ✓$	$8 \times 8 \times$
$\frac{n}{2} ✓$	$\frac{7}{2} \times$

How can we write an algebraic expression from a real-world situation? We have to begin with defining a variable. This means that we call any value, which we do not know or is constant, by any letter. We can form algebraic expressions with this variable or variables to fit the real-world situations.

Situation	Defining variables	Algebraic Expression
A museum entrance fee costs $$ 2$ for each child and $$ 3$ for each adult.	Let the number of children be $x$ and the number of adults be $y .$	$2 x + 3 y$
A group of friends want to go to the movies and each ticket costs $$ 8 .$	Let the number of friends be $f .$	$8 f$
Two friends want to share a pizza evenly between the both of them.	Let the number of slices for each friend be $n .$	$\frac{n}{2}$