well hmmm
let's say
b = amount of buzz cuts
f = amount of flat-top cuts
now, the total price for all the buzz cuts, since each one is $9, will then be 9*b or 9b
and the price for all flat-top cuts, since each is $13, will then be 13*f or 13f
one day Jerry made a total of $600, so we know, whatever "b" and "f" are, we know their price sum was 600,
thus 9b + 13f = 600
now, Jerry "knows that he cut three times as many buzzes as flat-tops", so, whatever "f" is, "b" is three times that much, or 3*f, so b = 3f
now then [tex]\bf \begin{cases}
9b+13f=600\\
\boxed{b}=3f\\
----------\\
9\left( \boxed{3f} \right)+13f=600
\end{cases}[/tex]
solve for "f"
