Set 1: Systems Of Equations (Intermediate)

**Choice B is the best answer.** Using elimination or substitution: x = 5

Explanation

Answer: B

PROBLEM

Solve: x + 4y = 21, 4x + 5y = 40. Find x.

✓ Correct

Detailed Explanation

Choice B is the best answer. Using elimination or substitution: x = 5

Why others are wrong:

A: 7 is incorrect because it does not satisfy the equation.

C: 4 is incorrect because it does not satisfy the equation.

D: 3 is incorrect because it does not satisfy the equation.