If 2x + 3y = 19 and 4x - 3y = 5, what is the value of 6x?

The $y$-terms $+3y$ and $-3y$ cancel when you add the equations: $(2x + 3y) + (4x - 3y) = 19 + 5$, so $6x = 24$. The question asks for $6x$, which is 24 directly, and no further solving is necessary. Check: $x = 4$, and then $y = 3.67$ from the first equation, and the second gives $16 - 11 = 5$. A common wrong answer is 4, which is $x$ rather than $6x$. Another is 14, from subtracting 5 from 19. Always look at the exact quantity requested, which here is the combined result of the elimination.