Explanation:
what I found and fits the given 3 elements is :
the difference between the top number and the left bottom number is multiplied by the right bottom number. the result is the number inside the triangle :
(7 - 2) × 2 = 5×2 = 10
(4 - 3) × 2 = 1×2 = 2
(14 - 9) × 4 = 5×4 = 20
with that same structure we have
(10 - 3) × 2 = 7×2 = 14