[Lebnany96]

Simultaneous Equations - Algebraic Methods
1. Five less than twice Michelle's present age is equal to Sandra's present age. Two years ago, twice Sandra's age was the same as ten years more than triple Michelle's age. Find the present ages of the two girls.

The answers are:(I just can't figure out how to do it?)
Michelle: 18
Sandra:31

[Curlyben]

Looks at the equations.
What do you have when you simplify them down ?

The statements give you two equations that just need solving.

[Lebnany96]

yeah I made two equations and solved them using substitution, but my answer didn't match the textbook one. I tried over and over to try and alter my equations, but I don't think its right? These is what I did:

Let x be Michelle
Let y be Sandra

2x-5=y (1)
2y-2=3x+10 (2)

Am I using the correct equations?

[Lebnany96]

Plzzzzzzzzzzzzzzzzzzzz HELP need answer asap :)

[Curlyben]

The problem is in the second equation.
Now it was TWO years ago that was true so, therefore BOTH ages where 2 years younger.

Does that make sense ?

[Lebnany96]

thanks a lot curlyben!! I'm not sure if this is right but this is what I tried:

what if I changed the second equation to:

2y-2 = 3x+10-2

but that doesn't work when I substitute the y ( y=2x-5)?
thanks so much for your help I'm still working on it

[Lebnany96]

omg I think I got it??

what about if:

I do 2y which is 2(2x-5) = 3x+10
that is 4x - 10 = 3x+10
add ten on both sides
minus 3x from both sides
x=20 (two years ago)
so minus 2 off that?
is that rite?
thanks so much for your help!

[Curlyben]

Bingo ;)
That's exactly what I was thinking.

Does that help you now..

[Lebnany96]

Thankyouu so much for your help it is MUCH APPRECIATED!!
I finally understand hahah :D

[Curlyben]

You where on the right track, just missed a subtle fact.

All good now ?

[Lebnany96]

Thanks very much! I'm all good now :)