Start: 3y+4y=6+15.

Now, here is another thing you can do. By just thinking "I have 3 apples and 4 apples, so I must have 7 apples" you can take the first step:

Start: 3y+4y=6+15

Add 3y+4y: 7y=6+15

OK? 3 times something + 4 times something = 7 times something. Just remember, they must all be the same something, like "apples". You cant add apples to rocks, so you cant add "x" to "y"

AND you didn't have to do it to BOTH sides, because you were just RE-ARRANGING things on one side, not adding anything.

Now, the next step is easy, just add the 6 and 15 together:

Start: 3y+4y=6+15

Add 3y+4y: 7y=6+15

Add 6+15: 7y=21

And then we use our "you can divide so long as you do it to both sides" rule, so let's divide BOTH sides by 7

Start: 3y+4y=6+15

Add 3y+4y: 7y=6+15

Add 6+15: 7y=21

Divide by 7: y=3 DONE !

It is just like a GAME or PUZZLE with rules.

]]>So "-6u=-30" means "-6 times something-I-dont-know-yet equals -30"

They want you to work out the "something-I-dont-know-yet" part

So, -6 times WHAT equals -30 ?? I can guess it is 5, because 6x5=30, but you aren't supposed to just GUESS, so there are some things you can do to get the right answer.

Think of it as a PUZZLE, that starts at "-6u=-30" and ends at "u=5", and the rules are:

* You can multiply or divide by anything so long as you do the SAME to both sides of the "="

* You can add or subtract anything so long as you do the SAME to both sides of the "="

So, here goes:

Start With: -6u = -30

Multiply BOTH sides by (-1): 6u = 30 (Read here about Multiplying Negatives)

Divide BOTH sides by 6: u = 5 DONE

1. -6u=-30

2. 3y+4y=6+15.]]>