<PRE><B>Question 743190</B>
The problem states:

Mrs johnson is buying supplies for her fifth grade class. Mechanical pencils cost 15 cents each and markers cost 25 cents each. If she spends $21 on these items, and buys 100 items in all, how many pencils and how many markers did she buy?

Let x = the number of mechanical pencils she bought
Let y = the number of markers she bought

We are given

.15x + .25y = 21.00
   x + y = 100
and x= 100 - y

substitute for x in equation one and we have

.15(100 - y) + .25y = 21.00
15 - .15y + .25y = 21.00
.10y = 6 and y = 60, so x = 40

checking our work

.15*40 + .25*60 = 21
6 + 15 = 21

so she bought 40 mechanical pencils and 60 markers

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