Solve the simultaneous equations x + y = 5 and 2x + y = 9. What is the value of x?

Answer and explanation

Correct answer: A. 4

  1. Step 1: Subtract the first equation from the second: (2x + y) - (x + y) = 9 - 5, so x = 4. Step 2. Check in the first equation: y = 5 - 4 = 1, and 2(4) + 1 = 9. Answer: 4. Why not the others: 1: That is the value of y, found from x + y = 5. 5: Subtracting the two equations gives x exactly; one more does not satisfy both equations. 3: Subtracting the two equations gives x exactly; one less does not satisfy both equations.

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