# Evaluating algebraic expressions

#### Everything You Need in One Place

Homework problems? Exam preparation? Trying to grasp a concept or just brushing up the basics? Our extensive help & practice library have got you covered.

#### Learn and Practice With Ease

Our proven video lessons ease you through problems quickly, and you get tonnes of friendly practice on questions that trip students up on tests and finals.

#### Instant and Unlimited Help

Our personalized learning platform enables you to instantly find the exact walkthrough to your specific type of question. Activate unlimited help now!

##### Intros
###### Lessons
1. i) What are variables?

ii) What is an expression?

##### Examples
###### Lessons
1. Below we have used ponds and tadpoles to model an expression. Write the expression and use the variable x to represent the unknown number of tadpoles in each pond.

2. Mary bought $s$ packages of stickers, and there are 10 stickers in each package. Write an expression to show how many stickers Mary bought.
1. Write an expression for each phrase. Then, evaluate the expression.
1. 10 pounds lighter than Molly (m), when m=100
2. 22 years older than Tracy (t), when t = 10.
3. 17 less than 5 times a number (n), when n = 7
2. Evaluate the following expression, if $x = 7$ and $y = 9$
1. $6x-y+5$
2. $\frac{2}{3}x+\frac{1}{6}y-1$
3. $0.5x-0.1+1.3y$
##### Practice
###### Topic Notes
In this section, we are given models of cups and counters and asked to write the expressions represented by these models. We then use the variable x to represent the number of counters in each cup. We were first taught how to write expressions and solve for variables in a previous section. In this section, we are also asked to draw cup and counter models of given expressions. Finally, we are asked to write expressions for given phrases and evaluate the expressions using our variables.