Algebra 2 (1st Edition)

$4$ electric and $5$ acoustic guitars were sold.
Let $x$ be the number of electric guitars sold. Then the number of acoustic guitars sold is $9-x$. Thus our equation is: $479x+(9-x)339=3611\\479x+3051-339x=3611\\140x=560\\x=4$ Thus $4$ electric and $5$ acoustic guitars were sold.