let
cost of each small box of tangerines = x
cost of each large box of tangerines = y
Joe sales
[tex]4x+12y=124[/tex]Maria sales
[tex]11x+3y=71[/tex]Therefore,
[tex]\begin{gathered} x+3y=31 \\ x=31-3y \\ \text{Therefore,} \\ 11(31-3y)+3y=71 \\ 341-33y+3y=71 \\ 341-30y=71 \\ -30y=71-341 \\ y=\frac{-270}{-30} \\ y=9 \\ \\ x+3y=31 \\ x+3(9)=31 \\ x+27=31 \\ x=31-27 \\ x=4 \end{gathered}[/tex]cost of one small box of tangerine = $4
cost of one large box of tangerine = $9