Three linear equations are given below

MATHEMATICS · Single correct · AoPS · Mathematics · Multi-Variable Linear Equations · Multi-Variable Linear Equations

Problem

Three linear equations are given below. (I)

2x + 7y = 5

(II)

3x - 7y = 11

(III)

5x + 4y = 12

Which pair of equations will allow immediate elimination of

y

by simply adding or subtracting the two equations without any scaling? (a)

\text{I and III}

(b)

\text{II and III}

(c)

\text{I and II}

(d) \text{None of these}