Need help with math

Question

Staples sells boxes of pens ($9) and rubber bands ($6). Leona ordered a total of 22 cartons for $180. How many boxes of each did Leona order? Hint: Let P = Pens.

Answer 1

p + r = 22

9p + 6r = 180

 

p = 22 - r

9(22 - r) + 6r = 180

198 - 9r + 6r = 180

-3r = -18

r = 6

 

p = 22 - 6

p = 16