Answer:
40
Step-by-step explanation:
The average of [tex]x[/tex] values with is equal to the sum of all of those values divided by [tex]x[/tex].
Therefore, we have the following equation:
[tex]\frac{28+43+a}{3}=37,\\28+43+a=37\cdot 3,\\28+43+a=111,\\a=111-43-28=\boxed{40}[/tex]
