let us say... . the machine sold packages of chips at the amount of "p",
and the machine also sold, last month as well, an amount of "c" candies
now, last month the machine sold total 298 items
that yielded a revenue of $139.80
so...whatever "p" and "c" are, we know that, their sum for last month is,
298, so,
p + c = 298
how much revenue in sales of chips? well, they're 0.40 per package,
so, whatever "p" is, the machine sold 0.40 p or 0.4p in revenue
how much for the candies? well, they're 0.50 for each, so
whatever "c" is, 0.50 c or 0.5c in revenue
we know, their total revenue yield was 139.80
so
0.4p + 0.5c = 139.8
now... do substitution from the 1st equation on the 2nd one, and solve for "p", or packages of chips
that is \(\begin{cases}
p+c=298\to c=\boxed{298-p}
\\ \quad \\
0.4p+0.5c=139.8
\\
\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\\
0.4p+0.5(\boxed{298-p})=139.8
\end{cases}\impliedby \textit{solve for "p"}\)
