Please help with simultaneous equations!

[ozzstriker]

Solve the following :

3y+2x =12
y =x-1

so I multiplief the first line by 2, and the second by 6 to get

6y+4x=24
6y-6x=-6 -

y+10x =30
x= 3

So the problem here now is finding y

If u used the equation y=x-1 then y would equal 2

But the answer booklet says y is 6???

 

[jwpaine]

Solve the following :

3y+2x =12
y =x-1

so I multiplief the first line by 2, and the second by 6 to get

6y+4x=24
6y-6x=-6 -

y+10x =30
x= 3

So the problem here now is finding y

If u used the equation y=x-1 then y would equal 2

But the answer booklet says y is 6???

I'll use substitution:

{3y+2x =12
{y=x-1

y=(x-1) so

3(x-1)+2x=12
so x = 3

plugin x=3 into either equation and solve for y
so y = 2


your book is wrong. You are correct. y = 2

 

[ozzstriker]

Thank you thank you so. It was doing me head in, I knew I was correct

 

[Denis]

Solve the following :
3y+2x =12
y =x-1

You're complicating it, ozzy; just substitute y = x-1 in 1st equation:
3(x - 1) + 2x = 12
3x - 3 + 2x = 12
5x = 15
x = 3