Writing Equations
The sum of a number x and 7 is 20
x + 7 = 20
x + 16 = 20: x=4
20 = 20
yes
z + 4 = 6
A teacher tells 36 students to form 4 equal groups. Write and solve a multiplication equation to find how many students s there should be in each group.
4x = 36
9 students in each group
Variable
A symbol that represents one or more numbers
p - 4 = 28 ; p=32
32 = 32
Yes
x - 5 = 20
x = 25
The Florida Panther has an average height of 30 inches. It is 20 inches taller than the Northern Mockingbird. Write and solve an equation to find the average height of the Northern Mockingbird.
x +20 = 30
x = 10
Evaluate
solve
A number c less than 12 is equal to 9
12 - c = 9
4x = 44 ; x=10
40 = 44
no
c/7 = 5
c = 35
You have been saving $12 each week for many weeks. One day, you decide to count your savings and find that you have $384. Write and solve a multiplication equation to find how many weeks w you have been saving.
12w = 384
w=32
Two numbers whose product is 1 or the opposite fraction
One half of a number v is 14
1/2v = 14
x2 + 4 = 14 ; x=5
29 = 14
no
4x=36
x = 9
The advertised price of a cell phone is $149 after a $50 mail-in rebate. Write and solve an equation to find the price of the cell phone before the rebate is applied.
x - 50 = 149
x=199
Inverse Operations
Opposite operations
A number x squared plus another number y squared equals 4
x2 + y2 = 4
x3 - 4 = 4 ; x=2
4=4
yes
(2/5)y = 8
y = 20
A 14-inch pepperoni pizza is sliced into 8 equal pieces. One slice contains 352 calories. Write and solve a division equation to find how many calories c there are in the whole pizza.
c/352=8
c = 2816
Solution
a value that makes an equation true