The value of $1+2+3-4+5+6+7-8+9+10+11-12$ is
(A) 30
(B) 42
(C) 54
(D) 65
(E) 78
We group the terms and start with addition, and then do subtraction:

$$
\begin{aligned}
& 1+2+3-4+5+6+7-8+9+10+11-12 \\
& =6-4+18-8+30-12 \\
& =2+10+18 \\
& =30
\end{aligned}
$$

ANswer: (A)