To find the sum $ v $ of the vectors $ v_1=(a_1, b_1) $ and $ v_2=(a_2, b_2) $ we use formula
$$ v = (a_1 + a_2, b_1 + b_2) $$In this example $ a_1 = 1 $ , $ b_1 = 2 $, $ a_2 = 3 $ and $ b_2 = 4 $, therefore:
$$ \begin{aligned}v &= (a_1 + a_2, b_1 + b_2) \\v &= \left(1 + 3, 2 + 4 \right) \\v &= \left(4,~6\right) \end{aligned} $$