SOLUTION: Hello and thank you, My question is..... can you give me step by step instructions on equations with two variables now for instance I can solve a question like this x=2y when x=

Question 85398: Hello and thank you,
My question is..... can you give me step by step instructions on equations with two variables now for instance I can solve a question like this
x=2y when x=0 that is easy. My question is when the questions are like this....
2x +2y when y=2 what is throwing me off is the fact that it has a number in front of the letter in both? am I making any sense? I have searched the internet and connot find any sample question that have "when x=2" or when x=0 (not necessarily having to be those particular numbers)
can you help? I hope my question didnt confuse you?
here is a sample question that if you solve for me I can plug into to solve the rest of my home work
Sample question: 2x+2y=4 When x=4
PLEASE HELP ME IM SOOO CONFUSED
Thank you
Renee
Answer by bucky(2189) (Show Source): You can put this solution on YOUR website!
The numbers in front just tell you to multiply that times the letter.
.
In your example:
.
2x+2y=4 When x=4
.
The x = 4 tells you to substitute 4 for the letter x and you get:
.
2*4 + 2*y = 4
.
(the * means multiplication)
.
But 2*4 (meaning 2 times 4) is equal to 8. So you can replace 2*4 with 8 and the equation
then becomes:
.
8 + 2*y = 4
.
In solving this equation we will have two goals. The first is to get the term with the
unknown letter by itself on one side of the equal sign and everything else on the other
side. Our second goal will be to solve for just a single +y and that will be our
answer.
.
Back to our equation. Note that there is an 8 on the side with the term containing
the letter y. Remember our first goal. We need to get rid of the 8. We can do that by
subtracting 8 from the left side. But a rule of equations is that whatever you do to one
side of the equation you must also do to the other side. So if we subtract 8 from the
left side, we have to subtract 8 from the right side also. When we subtract 8 from the
left side, the 8 is gone on that side. And subtracting 8 from the right side results in
the right side becoming 4 - 8. And when you do this subtraction you get the answer of
-4. So what we have left is:
.
2*y = -4
.
But the left side is 2*y and we need it to be just y. We can do that by dividing the left
side by 2. (Think ... 2*y divided by 2 is 1*y which we write as just y.) But remember
that if we divide the left side by 2, we must also divide the right side by 2. And the
right side division of -4 divided by +2 is -2. As a result of all this,
the final
answer we end up with is:
.
y = -2
.
Hope this helps you to understand problems of the type you are having difficulty with.
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