SOLUTION: I have tried but it has been way too long since i have done algebra. I can no longer even help a 5th grader with homework. Mrs johnson is buying supplies for her fifth grade cl

Question 743190: I have tried but it has been way too long since i have done algebra. I can no longer even help a 5th grader with homework.
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?
Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
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

RELATED QUESTIONS
Can you please help me solve problems such as {{{1/h 5th power = h nth power}}}. What is... (answered by Theo)

My daughter is struggling in algebra and it has been way to long since I have done it! We (answered by solver91311)

I am a Mom trying desperately to help my son with his homework. It has been along time... (answered by LilSkittleMd)

Can you please help me solve and graph y=x-2? It has been a very long time since I have... (answered by Alan3354)

My son and I have been working on his homework for a few hours now. I can solve the... (answered by ankor@dixie-net.com,stanbon)

I am trying to help my daughter with homework and apparently it has been too long since I (answered by mananth)

Help with this one too? This linear systems by substitution, i think this is a no... (answered by scott8148)

3t>6t+12 I'm trying to help my son with his algebra and it's been a long time since... (answered by nyc_function)

Hi there! I am a Parent who is in need of some assistance. It has been years since I've... (answered by tutor_paul)