Substitution Word Problems

Jacob bought a total of 9 pizzas for his class party. The amount of large pizzas was twice the amount of medium pizzas. How many large and how many medium pizzas did he buy?

What do the two variables in this problem stand for? Select two choices below.

• x = number of large pizzas

• y = number of medium pizzas

• x = numbers of students in Jacob's class

• y = how hungry the students are

• y = number of slices each student gets

Tags

CCSS.8.EE.C.8C

Jacob bought a total of 9 pizzas for his class party. The amount of large pizzas was twice the amount of medium pizzas. How many large and how many medium pizzas did he buy?

x = number of large pizzas

y = number of medium pizzas

Which of the two equations below represent this situation. Select two answers.

• x + y = 9

• x = 2y

• y = 2x

• xy = 9

Tags

CCSS.HSA.CED.A.3

Given our two equations:

x + y = 9

x = 2y

Which variable is already isolated?

• In equation 2, the x is isolated.

• In equation 1, the x is isolated.

• In equation 2, the y is isolated.

• In equation 1, the y is isolated.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Given that x = 2y, substitute it into the other equation. What equation do you have now?

• (2y) + y = 9

• x + (2x) = 9

• x + (2y) = 9

• 2y = 2y

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Use that equation to solve for y:

(2y) + y = 9

• y = 3

• y = 4.5

• y = 27

• y = 6

Tags

CCSS.7.EE.B.4A

Given that y = 3, use that information with one of the two equations to solve for x.

y + x = 9

x = 2y

• x = 6

• x = 1.5

• x = 3

• x = 12

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Remember:

x = the number of large pizzas

y = the number of medium pizzas

x = 6, y = 3

In the context of the problem, what is true? Select the two true statements below.

• Jacob bought 6 large pizzas.

• Jacob bought 3 medium pizzas.

• Jacob bought 6 medium pizzas.

• Jacob bought 3 large pizzas.

Tags

CCSS.8.EE.C.8C