Question

You went shopping for back to school and bought packs of pens and pencils. a pack of

Answer 1

Answer:

5 packs of pens and 8 packs of pencils.

Step-by-step explanation:

Let the Pn and Pl stand for the number of packs of pens (Pn) and pencils (Pl) purchased.

We know that each pack of pens is $3 and each pack of pencils is $2.50.

We are also told that Pn + Pl = 13  [In total, 13 packs were purchased].

And we're told that $35 was spent.

The $35 must equal:  $3*Pn + $2.5*Pl  [the sum of the number of packs of each times the price per pack for each]

 3*Pn + 2.5*Pl = 35

Rearrange the first equation:

Pn + Pl = 13

Pn = 13 - Pl

Use this definition of Pn in the second equation:

3*Pn + 2.5*Pl = 35

3*(13 - Pl) + 2.5*Pl = 35

39 - 3Pl + 2.5Pl = 35

-0.5Pl = -4

Pl = 8

8 packs of pencils (Pl) were purchased.

This means the packs of pens purchased must be 5, since a total of 13 packs were purchased.

Check:

Does 5 packs of pens and 8 packs of pencils total $35?

5*($3) + 8*($2.5) = $35  ??

$15 + $20 = $35  ?

YES

You bought  5 packs of pens and 8 packs of pencils.