Evaluating Variable Expressions

Order of operations

100

What does "PEMDAS" stand for?

P = parentheses E = exponents M = multiplication D = division A = addition S = subtraction

200

What does 8^2 (8 to the power of 2) mean?

8 times itself, or 8*8, or 64.

300

In the expression 6(7 + 9), which step should we start with according to PEMDAS?

7+ 9 = 16

400

Solve: 5(4^2 + 3)

5(16 + 3) = 5*19 = 95

500

Solve: 3(x + 9) - 3 ; use x = 4

3(4 + 9) - 3 = 3(13) - 3 = 39 - 3 = 36

Two-variable expressions

100

3(y + x) ; use x = 4, y = 0

3(4) = 12

200

4 + xy ; use x = 7 and y = 3

4 + 21 = 25

300

8(5 - x) - y ; use x = 3 and y = 12

8(5 - 3) - 12 = 8(2) - 12 = 16 - 12 = 4

400

(c + d) + 4(c) ; use c = 8, d = 9

(8 + 9) - 4(8) = 17 + 32 = 49

500

5(f - h) - 2h ; use h = –1, f = 2

5(2 - -1) - 2(-1) = 5(2 + 1) + 2 = 5(3) + 2 = 17

Distributive Property

100

Calculate: 4(3 + 2)

4(5) = 20

200

5(3 + x); use x = 3

5(3 + 3) = 5(6) = 30

300

x(2 + y); use x = 1, y = 7

1(2 + 7) = 9

400

x(y - 8); use y = 18, x = 10

10(18 - 10) = 10(8) = 80

500

u = 7, w = -3 Solve u(w - 8)

7(-3 - 8) = 7(-11) = -77

Sorting Like Terms

100

xy+3xy-5xy

-2xy

200

5n+9m-12n-13m

-7n-4m

300

-15y-8y+16+9x

-23y+16+9x

400

3ab+4ba-7-12

7ab-19

500

y(y ^ 3) + x ; use x = 3, y = 2

16 + 3 = 19

One-variable expressions

100

4(x) ; x = 12

48

200

-3y ; use y = -3

9

300

t/18 ; use t = 0

0

400

(5y - y)/2 ; use y = 6

(30 - 6)/2 = 24/2 = 12

500

(50 + g)/g ; use g = 10

6