Write the Expression
Five more than a number
x + 5
6x + 4x
10x
3x + 2, if x = 2
8
x + 9 = 21
x = 12
Each movie ticket costs $12. Write an expression for the cost of t tickets.
12t
Student says: 5x + 3x = 8
What is wrong?
They forgot to include the variable → 8x
Three times a number minus 4
3x - 4
10x - 2
5x − 6, if x = 3
9
4x = 28
x = 7
A gym charges $20 monthly plus $5 per class.
Write the expression.
20 + 5c
Student says:
4x = 20
x = 16
What is wrong?
They subtracted instead of dividing → x = 5
The difference between 20 and a number
20 - x
8 + 5x - 3
5x + 5
2x + 8 − x, if x = 4
12
9x - 7 = 29
x = 4
A taxi charges $6 base fee plus $3 per kilometer. The total bill was $24. How many kilometers was the ride?
6 kilometers
A student simplified:
4x + 3 + 2x − 5
6x − 2
4x
What went wrong?
They accidentally combined −2 with 6x. 6x − 2 cannot be simplified further because 6x and −2 are not like terms.
Double a number plus 7
2x + 7
9x − 4 + 2x − 6
11x - 10
3x - 9 + 2x, if x=11
46
7x − 4 = 3x + 16
x = 5
A phone plan charges $25 monthly plus $8 per GB of data. The bill was $89. How many GB were used?
8 GB of data
Student says:
6x − 3 = 3x + 12
6x − 3x = 12
3x = 12
x = 4
What is missing?
They forgot to move the −3 (should add 3 to both sides).
Four less than, three times a number divided by 2
(3x/2) − 4
6x² + 3x − 2x² + 5
4x² + 3x + 5
4x - 3 + 2x + 2, if x = 4
23
5x - 52 = 25 - 6x
x = 7
A fundraiser needs to raise $500. Right now, they have $100.They sell cards for $10 each. How do they need to sell to get $500?
40 cards
8x − 3 = 2x + 15
8x − 2x − 3 = 15
6x − 3 = 15
6x = 12
x = 2
What went wrong?
They subtracted 2x correctly, but they forgot to move the −3.
After 6x − 3 = 15, they must add 3 to both sides:
6x = 18
x = 3