Multiple choice general knowledge math & puzzles If 2x-y=4 then 6x-3y=? 15 12 18 10 Reveal answer Fill a bubble to check yourself B Correct answer Explanation If 2x - y = 4, then 6x - 3y = 3(2x - y) = 3 × 4 = 12. We can factor out 3 from 6x - 3y to get 3 times the given expression.