Equations in x and y: write one for a story, and check a solution pair

Answer Key - Grade 9 Math Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   Put 3 in the x place and 5 in the y place of 2x + y. In math club, Kira tests the pair (3, 5) in 2x + y = 12. What does 2x + y come to when x = 3 and y = 5?

   11
2. 2.

   Put 4 in the x place and 1 in the y place of 3x + y. On a worksheet, Luz tests the pair (4, 1) in 3x + y = 14. What does 3x + y come to when x = 4 and y = 1?

   13
3. 3.

   Put 5 in the x place and 3 in the y place of x + 2y. In a puzzle book, Tala tests the pair (5, 3) in x + 2y = 9. What does x + 2y come to when x = 5 and y = 3?

   11
4. 4.

   Put 3 in the x place and 5 in the y place of 4x + y. In the warm-up, Jun tests the pair (3, 5) in 4x + y = 17. What does 4x + y come to when x = 3 and y = 5?

   17
5. 5.

   The rule is 2x + y = 15. Pia knows 2x + y = 15 and x = 4. The row says 2 × 4 + y = 15, which is 8 + y = 15. What is y?

   7
6. 6.

   The rule is 3x + y = 14. Bo knows 3x + y = 14 and x = 2. The row says 3 × 2 + y = 14, which is 6 + y = 14. What is y?

   8
7. 7.

   The rule is 4x + y = 21. Milo knows 4x + y = 21 and x = 3. The row says 4 × 3 + y = 21, which is 12 + y = 21. What is y?

   9

8. Read this first

   Money for each item = price × count. Table

   count	money
   c	2c
   d	3d

9. 8.

   Kira buys c cookies at $2 each and d drinks at $3 each, and spends $21. The cookies cost 2c dollars. Which equation fits the whole story?

   • c + d = 21
   • 3c + 2d = 21
   • 2c + 3d = 21
10. 9.

    Ren buys s sticker sheets at $1 each and g gel pens at $4 each, and spends $17. The pens cost 4g dollars. Which equation fits the whole story?

    • 4s + g = 17
    • s + g = 17
    • s + 4g = 17
11. 10.

    Esme buys f fruit cups at $3 each and w water bottles at $2 each, and spends $19. The fruit cups cost 3f dollars. Which equation fits the whole story?

    • 2f + 3w = 19
    • f + w = 19
    • 3f + 2w = 19