L17 · Multi-step equations

1. 1.

   The equation 2x + 1 = 15 is true when x = 7. Check by substitution.

   Answer. checks (15 = 15)

   2(7) + 1 = 14 + 1 = 15.

2. 2.

   The equation 5x + 6 = 21 is true when x = 3. Check by substitution.

   Answer. checks (21 = 21)

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

3. 3.

   The equation 2x + 2 = 14 is true when x = 6. Check by substitution.

   Answer. checks (14 = 14)

   2(6) + 2 = 12 + 2 = 14.

4. 4.

   The equation 3x + 2 = 11 is true when x = 3. Check by substitution.

   Answer. checks (11 = 11)

   3(3) + 2 = 9 + 2 = 11.

5. 5.

   The equation 5x + 3 = 28 is true when x = 5. Check by substitution. Then Ava needs 2 of that amount. What is the total they need?

   Answer. checks (56 = 28)

   5(5) + 3 = 25 + 3 = 28. Then multiply by 2: checks (56 = 28).

6. 6.

   The equation 4x + 4 = 12 is true when x = 2. Check by substitution. Then Owen needs 2 of that amount. What is the total they need?

   Answer. checks (24 = 12)

   4(2) + 4 = 8 + 4 = 12. Then multiply by 2: checks (24 = 12).

7. 7.

   The equation 5x + 5 = 20 is true when x = 3. Check by substitution. Then Owen needs 4 of that amount. What is the total they need?

   Answer. checks (80 = 20)

   5(3) + 5 = 15 + 5 = 20. Then multiply by 4: checks (80 = 20).

8. 8.

   The equation 3x + 4 = 19 is true when x = 5. Check by substitution. Then Jonah needs 4 of that amount. What is the total they need?

   Answer. checks (76 = 19)

   3(5) + 4 = 15 + 4 = 19. Then multiply by 4: checks (76 = 19).

9. 9.

   The equation 4x + 4 = 16 is true when x = 3. Check by substitution. Then Luis needs 3 of that amount. What is the total they need?

   Answer. checks (48 = 16)

   4(3) + 4 = 12 + 4 = 16. Then multiply by 3: checks (48 = 16).

10. 10.

    The equation 2x + 3 = 19 is true when x = 8. Check by substitution. Then Ava needs 2 of that amount. What is the total they need?

    Answer. checks (38 = 19)

    2(8) + 3 = 16 + 3 = 19. Then multiply by 2: checks (38 = 19).

11. 11.

    Think

    Nora tried this problem:
    The equation 5x + 4 = 24 is true when x = 4. Check by substitution.
    Nora wrote checks (-24 = 24). That is not correct. What is the right answer?

    Answer. checks (24 = 24)

    Nora’s answer checks (-24 = 24) is off. 5(4) + 4 = 20 + 4 = 24.

12. 12.

    Think

    Owen tried this problem:
    The equation 2x + 4 = 16 is true when x = 6. Check by substitution.
    Owen wrote checks (32 = 16). That is not correct. What is the right answer?

    Answer. checks (16 = 16)

    Owen’s answer checks (32 = 16) is off. 2(6) + 4 = 12 + 4 = 16.

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