Puzzle: Finding the next number in the sequence of numbers

Question

I'm trying to solve this puzzle and couldn't come up with the next value

Answer 1

Usually these puzzles want you to combine two of the numbers to get the third.

That is, $f(a,b)=c$, where $f$ combines common operations $+,-,\times,\div,\sqrt\space,\dots$

Notice that if $a\in\{93,72\}$ and $b\in\{63,44\}$ decrease, so does $c\in\{39,29\}$.

My first guess was that addition $+$ was used, but the result was too large. To fix this, I added division $\div$ by a constant $4$. This turned out to work out. $$\frac{93+63}{4}=39, \qquad \frac{72+44}{4}=29, \qquad \frac{47+13}{4}=15.$$