L22 · Two-variable relationships

1. 1.

   The rule is y = 3x + 7. What is y when x = 7?

   Answer. 28

   y = 3(7) + 7 = 21 + 7 = 28.

2. 2.

   The rule is y = 4x + 6. What is y when x = 3?

   Answer. 18

   y = 4(3) + 6 = 12 + 6 = 18.

3. 3.

   The rule is y = 3x + 6. What is y when x = 5?

   Answer. 21

   y = 3(5) + 6 = 15 + 6 = 21.

4. 4.

   The rule is y = 2x + 1. What is y when x = 4?

   Answer. 9

   y = 2(4) + 1 = 8 + 1 = 9.

5. 5.

   The rule is y = 4x + 5. What is y when x = 7? Then Jonah needs 4 of that amount. What is the total they need?

   Answer. 132

   y = 4(7) + 5 = 28 + 5 = 33. Then multiply by 4: 132.

6. 6.

   The rule is y = 5x + 7. What is y when x = 3? Then Sam needs 5 of that amount. What is the total they need?

   Answer. 110

   y = 5(3) + 7 = 15 + 7 = 22. Then multiply by 5: 110.

7. 7.

   The rule is y = 3x + 2. What is y when x = 6? Then Jonah needs 5 of that amount. What is the total they need?

   Answer. 100

   y = 3(6) + 2 = 18 + 2 = 20. Then multiply by 5: 100.

8. 8.

   The rule is y = 5x + 5. What is y when x = 5? Then Malik needs 2 of that amount. What is the total they need?

   Answer. 60

   y = 5(5) + 5 = 25 + 5 = 30. Then multiply by 2: 60.

9. 9.

   The rule is y = 6x + 3. What is y when x = 2? Then Malik needs 4 of that amount. What is the total they need?

   Answer. 60

   y = 6(2) + 3 = 12 + 3 = 15. Then multiply by 4: 60.

10. 10.

    The rule is y = 6x + 5. What is y when x = 6? Then Jonah needs 4 of that amount. What is the total they need?

    Answer. 164

    y = 6(6) + 5 = 36 + 5 = 41. Then multiply by 4: 164.

11. 11.

    Think

    Theo tried this problem:
    The rule is y = 6x + 7. What is y when x = 3?
    Theo wrote -25. That is not correct. What is the right answer?

    Answer. 25

    Theo’s answer -25 is off. y = 6(3) + 7 = 18 + 7 = 25.

12. 12.

    Think

    Sam tried this problem:
    The rule is y = 6x + 5. What is y when x = 4?
    Sam wrote 58. That is not correct. What is the right answer?

    Answer. 29

    Sam’s answer 58 is off. y = 6(4) + 5 = 24 + 5 = 29.

Original extra practice. Keys are computed from the items, not guessed.