L4 · Algebraic expressions

1. 1.

   Evaluate 7x + 8 when x = 7.

   Answer. 57

   7(7) + 8 = 49 + 8 = 57.

2. 2.

   Write an expression for “2 more than 6 times a number k.”

   Answer. 6k + 2

   6 times k is 6k; 2 more is 6k + 2.

3. 3.

   Evaluate 6x + 8 when x = 8.

   Answer. 56

   6(8) + 8 = 48 + 8 = 56.

4. 4.

   Write an expression for “5 more than 6 times a number k.”

   Answer. 6k + 5

   6 times k is 6k; 5 more is 6k + 5.

5. 5.

   Evaluate 8x + 4 when x = 8. Then Elena needs 3 of that amount. What is the total they need?

   Answer. 204

   8(8) + 4 = 64 + 4 = 68. Then multiply by 3: 204.

6. 6.

   Write an expression for “9 more than 3 times a number k.” Then Grace needs 4 of that amount. What is the total they need?

   Answer. 12k + 9

   3 times k is 3k; 9 more is 3k + 9. Then multiply by 4: 12k + 9.

7. 7.

   Evaluate 6x + 11 when x = 8. Then Theo needs 3 of that amount. What is the total they need?

   Answer. 177

   6(8) + 11 = 48 + 11 = 59. Then multiply by 3: 177.

8. 8.

   Write an expression for “4 more than 4 times a number k.” Then Theo needs 3 of that amount. What is the total they need?

   Answer. 12k + 4

   4 times k is 4k; 4 more is 4k + 4. Then multiply by 3: 12k + 4.

9. 9.

   Evaluate 7x + 4 when x = 7. Then Luis needs 3 of that amount. What is the total they need?

   Answer. 159

   7(7) + 4 = 49 + 4 = 53. Then multiply by 3: 159.

10. 10.

    Write an expression for “11 more than 4 times a number n.” Then Elena needs 2 of that amount. What is the total they need?

    Answer. 8n + 11

    4 times n is 4n; 11 more is 4n + 11. Then multiply by 2: 8n + 11.

11. 11.

    Think

    Nora tried this problem:
    Evaluate 8x + 5 when x = 2.
    Nora wrote -21. That is not correct. What is the right answer?

    Answer. 21

    Nora’s answer -21 is off. 8(2) + 5 = 16 + 5 = 21.

12. 12.

    Think

    Nora tried this problem:
    Write an expression for “2 more than 7 times a number x.”
    Nora wrote 14x + 2. That is not correct. What is the right answer?

    Answer. 7x + 2

    Nora’s answer 14x + 2 is off. 7 times x is 7x; 2 more is 7x + 2.

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