You didn’t state which one of these numbers is the base and the height which is needed to solve this problem.
If 14.3 is the base, and 12 is the height, then you multiply them and get the answer.
14.3 x 12 = 171.6
If 14.3 is the base and 18.4 is the height, multiply them.
14.3 x 18.4 = 263.12
So depending on which one is the base, or the height, the answer would be one of those two.
For your understanding of problems like this, the formula for solving the area of a parallelogram is base times the height.
Hope this helped :)