Let P be the cost of a box of pretzels and C be the cost of a bag of candy.
The cost of 4 boxes of pretzels is 4P, and the cost of 6 bags of candy is 6C. Since Angela sold 4 boxes of pretzels and 6 bags of candy, raising $108, then:
[tex]4P+6C=108[/tex]Similarly, from Kevin's information we can conclude that:
[tex]6P+2C=92[/tex]These two equations lead to a 2x2 system of equations. To solve it, isolate C from the second equation:
[tex]\begin{gathered} C=\frac{92-6P}{2} \\ \Rightarrow C=46-3P \end{gathered}[/tex]Then, substitute the expression for C into the first equation:
[tex]4P+6(46-3P)=108[/tex]Solve this equation for P:
[tex]\begin{gathered} \Rightarrow4P+276-18P=108 \\ \Rightarrow-14P+276=108 \\ \Rightarrow-14P=108-276 \\ \Rightarrow-14P=-168 \\ \Rightarrow P=\frac{-168}{-14} \\ \Rightarrow P=12 \end{gathered}[/tex]Substitute P=12 into the expression for C to find its value:
[tex]\begin{gathered} C=46-3(12) \\ =46-36 \\ =10 \end{gathered}[/tex]Therefore, a box of pretzels is worth $12 and a bag of candy is worth $10.