Linear Equation from Context

A tub has 40 gallons of water in it and starts draining at a rate of 6 gallons per minute. Write a formula for the amount of water left in the tub.

• y = 6x + 40
• y = -6x + 40
• y = 6x - 40
• y = 40x - 6

A mechanic charges a flat fee of $15 and then charges $65 per hour. Write a formula for the total cost of hiring the mechanic.

• y = 15x + 65
• y = 65x + 15

A candle is originally 12 inches tall and burns a constant rate of 2 inches per hour. Write a formula for the height of the candle remaining.

• y = 2x + 12
• y = -2x + 12
• y = 12x - 2
• y = 12x + 2

To prepare for a recent road trip, Jill filled up her 19-gallon tank. She estimates that her SUV will use about three gallons per hour. Write an equation to model the amount of gasoline, G, remaining in her tank after t hours.

• G=19 – 3t

• G=19 + 3t

• G=3 - 19t

• G=3 + 19t

Charlie rented a moving truck. He paid a daily fee plus a per-mile fee to rent the truck. The equation below represents the daily amount Charlie paid for the truck if he drives it x miles.
y=0.5x+10
What does the slope of the graph of this equation represent?

• The daily fee for the moving truck
• The per-mile fee for the moving truck
• How much Charlie paid for the truck
• The number of miles he drove

Rich is a member of a gym. He pays a monthly fee plus a per-visit fee. The equation below represents the monthly amount Rich pays for his membership to the gym per month for x visits.
y=3x+10
What does the y-intercept of the graph of this equation represent?

• The monthly fee
• How much Rich pays per visit
• The number of times Rich goes to the gym
• The total cost at the end of the month

Bob's Plumbing charges $25 per hour plus a service fee of $40 for coming out to your house. Which equation models this situation?

• y = 25x + 40

• y = 40x + 25

• y = 25x

• y = 25x - 40

Eddie's Electric charges $90 per hour plus a $50 traveling fee. Which equation models this scenario?

• y = -50x + 90

• y = 90x + 50

• y = -90 - 50x

• y = 50 - 90x

Amelia has $100 in her savings account and plans on saving $20 per week. Write an equation to represent this situation.

• y = 100x

• y = 20x

• y = 20x + 100

• y = 100x + 20

A plant is 5cm tall and growing at a rate of 3cm a month.

• y = 5 - 3x

• y = 5x + 3

• y = 3x +5