Algebra? Can anyone help with the answers to these questions?

[SecondhandRose]

DS has done algebra homework in preparation for his 11+ on the 30th. Can anyone tell me if his answers are right please?

QUESTION ANSWER
9x + 1 = 5x + 9 4x =8 1x =2

9X - 11 = 3x + 13 6x =24 1x =4

6x - 5 = 4x + 7 2x = 12 1x =6

11x - 26 = 10x +18 1x = 46

12x - 16 = 7x-1 5x = 15 1x = 3

There are a few more for checking too!

Oh, it's come out all squished together.
First one there should be a big space between the 9 and 4. Hope this makes sense to someone other than 10 and 11 year olds.

I think the 4th one is x = 44

others are right though.

Yes I agree - the others are right but no 4 is 44!

Call me sad but I quite enjoyed that!

me too hehehe I used to love algebra!

Thanks ever so much, how about these last few?

9x - 19 = 2x - 5
answer 7x=14 1x=2

7x +14 = 5x + 20
answer 2x=34 1x=17

9x +18 = 4x + 48
answer 5x=30 1x=6

11x +22 = 9x +36
answer 2x=14 1x=7

12x +12 = 7x +42
answer 5x=30 1x=6

Any chance you can explain how to work them out?

bump

Sorry - was having my tea!

Anyway back to business - number 2 isnt right I dont think but the others are.

How are they written before you have got the answer?

Please can someone tell me how to do these? I used to be good at maths, and have just discovered that I haven't a clue how to do algebra!

I can work them out if I am given the value of x - but only if it is right IYSWIM!

I can check that they are right, too, but it is really going to bug me that I can't actually work out the answer!

I can check that they are right, too, but it is really going to bug me that I can't actually work out the answer!

Yes I agree! There must be a way!

I think the answer to number 2 is 3.

Just through process of elimination! No formula that I have worked out!

OK
7x + 14 = 5x + 20 so
7x - 5x = 20 - 14 so
2x = 6 so
x = 3

Ok I think I have it

make it 7x - 5x = 20-14

so 2x = 6 1x = 3

??????

Can see how you got 34 by putting 14 + 20.

You swap the Xs and numbers across the sides so all the Xs are on one side of the = nd the numbers on the other(remembering that they switch sign when you move them across).

Hey I was right then SoupDragon!

I was determined to solve it!

hehehe

To work it out:

You move all the x stuff to the left of the =, and all the absolute values to the right. As anything crosses sides it changes from + to - or vice versa. Then you will have a multiple of x = an absolute value. You then divide the absolute value by the multiple of x.

Does that make any sense?

Thankyou, I had just looked it up, but you both explained it brilliantly.

I just can't believe I had completely forgotten it all

oops x cross posted

So out of the second lot I posted are they all right except 7x + 14 ?

Thanks - it's too late, I'm not capable of working them out myself.