# Pre algebra problem

• Feb 24th 2013, 05:03 PM
Th03
Pre algebra problem
Mrs jones gives \$680 each year to charity. She gives the united way twice as much as the Red Cross but only half as much as the American heart association. How much does she give to the American heart association? I get to 2x+x+1/2x=680. But I get confused because of the 1/2 so I have no idea how to solve it.
• Feb 24th 2013, 05:06 PM
chiro
Re: Pre algebra problem
Hey Th03.

Can you collect all the x terms to get an equation ax=b for real numbers a and b? (Also consider multiplying both sides by 2 to get rid of the fractions).
• Feb 24th 2013, 05:09 PM
Th03
Re: Pre algebra problem
3x+1/2x=180. I just don't know what to do with the 1/2. It confuses me. If it was a whole number I could finish it. But you say multiply the side by two to get rid of a fraction. Why am I able to do that? It just doesn't make sense why I can do that. Thanks for the help
• Feb 24th 2013, 05:22 PM
chiro
Re: Pre algebra problem
Multiplying both sides by a constant will preserve the equality. With regards to the half, 3x + 1/2x = 3.5x = 180 so x = 180/3.5
• Feb 24th 2013, 05:37 PM
Th03
Re: Pre algebra problem
Oh I see what you mean. I multiplied all sides by 2 and got the same answer as 680/3.5x. Thank you for the help