[lisaly]

Originally Posted by linz06

I wrote this down quickly so I'm not sure if it's the right answer but it was a nice quick break from work (I love math, I'm a geek)

Since you know what y is, you insert that value for y and you get:

-1/2-3 = 3/4x-8

First, you need common denominators if you want to add/subtract fractions. since the only fraction we need to worry about right now has a 2 on the bottom, put a 2 on the bottom of the other numbers we need to add an subtract. 3 becomes 6/2 and 8 becomes 16/2. Same value, just a common denominator. I'll put brackets around the fractions so they're easier to decipher in computer type. You end up with:

-(1/2) - (6/2) = (3/4x) - (16/2)

Now you can easily simplify the left side. You add or subtract the top numbers, so -1 - 6 = -7. Your new value for that side becomes -7/2:

-7/2 = (3/4x) - (16/2)

Simply add the 16/2 to both sides, which cancels it out on the right side and adds it to the left side. The bolded numbers cancel each other out and equal 0:

-(7/2) + (16/2) = (3/4x) - (16/2) + (16/2)

Add the -7 + 16 to end up with 9/2 on the left side:

9/2 = 3/4x

If you multiply 4x (in fraction form, 4x/1), the 4x will cancel out on the right side:

(9/2) * (4x/1) = (3/4x) * (4x/1)

When multiplying fractions, you can multiply straight across - top number times top number, over bottom number times bottom number. 9 * 4x = 36x, and 2 * 1 = 2. You end up with 36x/2:

36x/2 = 3

Now you can divide 36 by 2 and you end up simplifying to 12x:

12x = 3

To get x alone, you must divide both sides by 12:

x = 3/12, or simplified to x = 1/4

Originally Posted by mileydog

Actually it is wrong. X=6


9/2 = 3/4x

Up to this point you are correct.

However you simply need to multiply by 4 not 4x.

Thus you should get 36/2 = 3x
Simplified is 18 = 3x
18/3 = X
X=6

If you multiply 4x (in fraction form, 4x/1), the 4x will cancel out on the right side:

(9/2) * (4x/1) = (3/4x) * (4x/1)

When multiplying fractions, you can multiply straight across - top number times top number, over bottom number times bottom number. 9 * 4x = 36x, and 2 * 1 = 2. You end up with 36x/2:

36x/2 = 3

Now you can divide 36 by 2 and you end up simplifying to 12x:

BTW...Dividing 36x/2 gives 18x NOT 12x

12x = 3

To get x alone, you must divide both sides by 12:

x = 3/12, or simplified to x = 1/4

I think there is a much simpler way to do this problem. There are too many opportunities for mistakes with having the same denominator, and there's no need in this problem. If you need me to talk you through it by phone, I'd be happy to help. I've done it many times with my students and their parents when they are struggling at home.

set both y values to equal
-3 1/2 = 3/4x-8
add 8 to both sides

5 1/2 = 3/4x
multiply both sides by 4 to get rid of the denominator
11/2 x 4 =3x
21=3x
x=7

check:
-2.5=3/4x -8
add 8 to both sides

5.5=3/4 x7
5.5=21/4
5.5=5.5