Algebra practice question

Answer: 1

Parallel lines require c/3 = 2/6, so c = 1. The constants 10 and 21 are not in that 1:3 ratio, so the lines never meet.

Common wrong answers

If you answered 2

c = 2 gives slopes −1 and −1/2, which differ, so the lines would intersect.

If you answered 3

3 matches the x-coefficients directly, but the proportion must hold across both variables: c/3 = 2/6.

If you answered 10/7

10/7 forces the constants into proportion — that would give infinitely many solutions if the coefficients also matched, not none.

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