Staples sells boxes of pens for ($10) and rubber bands for ($4). Leona ordered a total of 24 cartons for $210. How many boxes of each did Leona order? Hint: Let P = Pens.

Form two simultaneous equations with the information provided:

10P + 4R = 210, P = no. of boxes of pens, R = number of boxes of rubber bands

10 is the cost of a box of pens; multiply this by P will give you the total cost of all the boxes of pens bought.

4 is the cost of a box of rubber bands; multiply this by R will give you the total cost of all the boxes of rubber bands bought.

We can also say:

P + R = 24, as 24 boxes (cartons) were bought in total.

Solve simultaneously:

P = 24 - R

Sub' this into 10P + 4R = 210 to give:

10 (24 - R) + 4R = 210

240 - 10R + 4R = 210

-6R = - 30

R = 5

and so:

P = 24 - (5) = 19

19 boxes of pens

5 boxes of rubber bands