Variable Basics
What is a symbol (such as a letter or a box) that represents an unknown number called?
A variable
Solve for x: x + 5 = 12
x = 7
y = 4
Solve for x: 5x - 14 = 8x + 4
x = -6
Jane has 8 clients but 2 canceled. If she walks dogs 7 days a week, write an expression for how many walks she did.
(8 - 2) x 7 = 42
In the expression 7 + x = 5, what does the "x" represent?
The unknown variable/number
Solve for y: y - 8 = 10
y = 18
Solve for x: x / 2 = 6
x = 12
Solve for y: y - 1 = 5y + 3y -8
y = 1
Melissa has 109 cupcakes for a bake sale and packs them into boxes of 6. How many full boxes can she make? What equation did you use?
Answer: 18 full boxes
True or False?
In 3 x y, the "y" means you multiply by three, but you don't know what "y" is yet.
True
Solve for x: 15 + x = 25
x = 10
Solve for y: 4y = 20
y = 5
Solve for x: 6 = 1 - 2x + 5
x = 0
A baseball stadium holds 5,000 fans. There are 2,600 Tigers fans and (x) Pirates fans. If the stadium is full, how many Pirates fans are there? What equation did you use?
Equation: 2,600 + x = 5,000
Answer: 2,400 Pirates fans
Replace the "?" with a letter variable.
3 + ? = 9
3 + x = 9
Solve for y: y - 12 = 12
y = 24
Solve for x: x / 5 = 10
x = 50
Solve for y: -(7 - 4y) = 9
y = 4
Juan owns 12 sets of football cards. If he has 336 cards in total, how many cards are in each set? What equation did you use?
Answer: 28 cards per set
Write the expression for "five more than a number"
x + 5
Solve for x: x + 150 = 300
x = 150
Solve for y: 12 x y = 0
y = 0
Solve for x: 2(4x - 3) - 8 = 4 + 2x
x = 3
Three less than half a number is nine. What is the number? What equation did you use?
Equation: x/2 - 3 = 9
Answer: x = 24