Originally Posted by

**whitedawg** **I'm having some trouble with simultaneous equations when all the letters are not on one side, I'm using the substitution method as I know this will help when moving onto quadratic equations. I'll give you an example question and show some of my workings. If someone could point out where Im going wrong and point me in the right direction i'd appreciate it. **

3x + 2Y - 14 = 0

2x + 16 = 5Y

I'd begin by getting rid of the 14 in equation 1 so

3x + 2Y = 14

Then taking 5Y off of the right side of equation 2 and 16 off the left giving

2x - 5Y = -16

Now I'll try to isolate either the X or the Y, in this case I'll choose the X from equation 1, so:

X = 3(14-2Y)

X = 42-6Y

And put that into equation 2. So,

2(42-6Y) - 5Y = -16

84 - 12Y - 5Y = -16

Then I add 84 to the left and right side of the equation

Now I dont know what the hell goes on.

I can do:

12Y - 5Y = - 100

7Y = 100

Y=14.2 - WRONG

-12Y - 5Y = -17Y

-17Y = 100 WRONG.

Im at a loss, I can do all other simultaneous equations. But when the letters start crossing sides I seem to get lost. I'm workin by the rule that whatever you do to one side you do to the other. ITS TWISTING MY MELON MAN.

I'd be greatful for your help, if you can explain where Im going wrong please.