Mark M. answered 03/27/20
Retired Math prof with teaching and tutoring experience in trig.
Draw the vector (arrow) from (0,0) to (2,-3). Draw the vector from (0,0) to (1,4). Construct the parallelogram with those vectors as two of its sides. Then, a+b is the the vector from (0,0) to (3,1), which lies along a diagonal of the parallelogram.