Question

Three pens and two notebooks cost 8.25. two pens and three notebooks cost $8.00. how much would two pens and two notebooks cost?

Answer 1

3p + 2n = 8.25 ....multiply by 2
2p + 3n = 8 .........multiply by -3
-------------------
6p + 4n = 16.5 (result of multiplying by 2)
-6p - 9n = - 24 (result of multiplying by -3)
-------------------add
-5n = - 7.5
n = -7.5 / -5
n = 1.50 .............notebooks cost 1.50 each

2p + 3n = 8
2p + 3(1.50) = 8
2p + 4.50 = 8
2p = 8 - 4.50
2p = 3.50
p = 3.50/2
p = 1.75......pens cost 1.75 each

so 2 pens and 2 notebooks cost : 2(1.75) + 2(1.50) = $ 6.50 <==