2-7 Variables and Expressions a letter that stands for a number; the value of a variable can change  Ex.  w + 3  w is the variable  6 + t What is the variable?  r  12 What is the variable? Constant - a number without a variable  Ex. w + 3  3 is the constant  6 + t What is the constant?

Expression - a mathematical phrase with variables, constants, and operations (there is no equals sign)   Ex. w + 3      6t  3y 45 Write three examples of expressions.

Here is how to represent each operation in algebra: Addition:  w + 3 Subtraction:  4  p    7 + y    x  12 Multiplication:  3 m Division:  12  j     4t    x    4(5)

Part 1: Write the operation shown. 2.) 3   x _____________________ 3.) 3 y _____________________ 4.) 3(-7) ______________________

times product - less than fewer than decreased by difference +   + more than greater than increased by sum   - less than fewer than decreased by difference    times product quotient divided by

1.) 5 more than y apples 3.) The product of 4 and w Write an expression for each word phrase. 1.) 5 more than y apples 2.) 8 less than the number x 3.) The product of 4 and w 4.) The sum of 9 and b 5.) The quotient of 7 divided by a

Applications 1.) Vicki and Tamra are working on their math homework together. Vicki has worked p problems and Tamra has worked 3 times as many as Vicki. a.) Write an expression for the number of problems Vicki has worked on b.) Write an expression for the number of problems Tamra has worked on c.) Write an expression for the total number of problems Vicki and Tamra have worked on 2.) Each shirt cost $12. Write an expression for the cost of n shirts.

Demonstrate Understanding Write the operation shown. 2.) 1.) -4w __________ Write an expression for each phrase. 3.) r more than 8 people 4.) 7 less than the number y 5.) The product of -7 and m 6.) The sum of 5 and w 7.) Frank had 7b baseball cards and his brother had b baseball cards. They combined their cards, and then gave away 2b cards. Write an expression to show how many they have left.