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WAEC Mathematics 2020 Question 10

Question 10

Linear and Simultaneous Equations

Solve 3x − 2y = 10 and x + 3y = 7 simultaneously.

  1. A.x = −4 and y = 1
  2. B.x = −1 and y = −4
  3. C.x = 1 and y = 4
  4. D.x = 4 and y = 1
Show the answer and explanation

Answer: D (x = 4 and y = 1)

Explanation

From the second equation x = 7 − 3y. Then 3(7 − 3y) − 2y = 10 gives 11y = 11, so y = 1 and x = 4.