There are \(12 - 2 + 1 = 11\) terms.
The first term is \(2 ( 2 ) - 1 = 3\).
The last term is \(2 ( 12 ) - 1 = 23\).
The sum equals the sum of the first and last term multiplied by half the number of terms.
\(S = ( 3 + 23 )\left( \frac{11}{2}\right) = ( 13 )( 11 ) = 143\)