chair                  desk                  
     1) Let x = the number of chairs,

           y =  the number of desks,  

           z = the number of filing cabinets.

                                       x + y + z = 330

                                        12x + 14 y + 15 z = 4500

                                        x - z = 20

Set up a matrix, and use inverse matrices to find the answer.

 A inverse * B

x = 100,  y = 150,   z = 80


m&m's

       

  2) Let   x = Number of Cokes,
            y = number of donuts,
            z = the number of bags of m&m's.

  x + 2y + z = 2.50
 3y + 2z = 2.25
  x + y + 2z = 3

Set up a matrix and then use inverse matrices to solve.

A inv*B = X

Coke is $1.25, donuts are $.25, and m&m's are $.75

Yes they have enough.