# Help !

• Jan 4th 2013, 11:29 AM
fsiwaju
Help !
Hello,

I am trying to solve this equation:
7x + 3y = 12
3x + 7y = 6

If x and y satisfy the system of equations above, what is the value of x-y?

I have tried really hard to solve this, I am appalling bad at Math ! Any help would be appreciated..
• Jan 4th 2013, 11:35 AM
MarkFL
Re: Help !
Using elimination, we could multiply the first equation by 3 and the second by -7 to get:

\$\displaystyle 21x+9y=36\$

\$\displaystyle -21x-49y=-42\$

Now, add the equations to eliminate x, and then solve for y. Then plug in this value for y into either original equation to find x.

What do you find?
• Jan 4th 2013, 11:50 AM
vjdm
Re: Help !
easy way to find x-y in this question is just subtract 2nd equation from 1st and then divide the whole by 4
7x-3x+3y-7y=12-6
4x-4y=6
x-y=6/4
x-y=3/2
• Jan 4th 2013, 12:04 PM
MarkFL
Re: Help !
LOL, I misread the question, I thought the OP was wanting to find (x,y), not x - y. :D
• Jan 4th 2013, 12:13 PM
fsiwaju
Re: Help !
Thanks guys !