8th Grade Equations: Master Variables & Linear Relationships

A store sells pencils for $0.50 each. If you buy x pencils, and your total cost is $10, what equation can you write to find x?

• 0.50 + x = 10

• x - 0.50 = 10

• 10 / x = 0.50

• 0.50 * x = 10

Maria has 3 times as many marbles as John. If John has y marbles, write an equation to express the number of marbles Maria has.

• 4y

• 3y

• y

• 2y

A car rental company charges a flat fee of $20 plus $0.15 per mile driven. If you drove m miles and paid a total of $50, what equation represents this situation?

• 20 + 0.15m = 60

• 20 + 0.15m = 40

• 20 + 0.15m = 30

• 20 + 0.15m = 50

A school is planning a field trip. The cost per student is $15, and there are s students attending. Write an equation to find the total cost of the trip.

• total cost = 15 + s

• total cost = 15 / s

• total cost = s - 15

• total cost = 15 * s

Tom is 4 years older than his sister. If his sister is a years old, write an equation to express Tom's age.

• Tom's age = a + 4

• Tom's age = a + 1

• Tom's age = a + 2

• Tom's age = a - 4

A recipe requires 2 cups of flour for every 3 cups of sugar. If you have f cups of flour, how many cups of sugar, s, do you need? Write the equation that relates f and s.

• s = f + 3

• s = (3/2) * f

• s = 2 * f

• s = (2/3) * f

A bike shop sells bikes for $200 each. If you buy b bikes, and your total cost is $800, what equation can you write to find b?

• b = 6

• b = 8

• b = 2

• b = 4

In a class, the number of boys is twice the number of girls. If there are g girls, write an equation to express the number of boys in the class.

• 3g

• 2g

• g

• g/2

A gardener is planting flowers in rows. If each row has r flowers and there are 5 rows, write an equation to find the total number of flowers, f, planted.

• f = r + 5

• f = 5 - r

• f = r / 5

• f = 5 * r

A concert hall has 300 seats. If x seats are sold, how many seats are still available? Write an equation to represent the number of available seats.

• 300 + x

• x - 300

• 300 - x

• 300 * x