math question,?

Question

solve for y;
7x + y = 13

&

3x +5y = 15

so im kinda stuck; ive been looking in my workbook, but couldnt find out how to do these equations, if you know how can you guys teach me(;?

Answer 1

If all you need to do is solve for y, then you want to isolate y on one side of the equation.

7x + y = 13

Subtract 7x from both sides (since it's bothering y).
y = - 7x + 13

y is all alone, so this one is done.


3x + 5y = 15

Subtract 3x from both sides.
5y = -3x + 15

Since 5y means 5 times y, you want to divide both sides by 5 (division is the opposite of multiplication).
y = -3x/5 + 15/5

y = -3x/5 + 3

I'm guessing that soon you will be heading into graphing straight lines in the form y =mx +b


y and x are any point one the line, m is the slope and b is the y-intercept.

b is where you start each line, in the first line you would go to y = 13 on the y axis and place your first point. Then since your slope is -7 or -7/1 as a fraction. You would count down seven spaces (negative slope means go down hill from left to right) and over one space to the right; this is your next point on the line. Keep going down 7 and over one, and connect the points to graph your line. I suggest three points, helps you line-up your ruler.

Answer 2

you know, i know this is a very easy equation, but i too am stuck... i dont know if u can do it, find one number... Everything is simplified...

You could get rid of 7x by dividing it into 13, but then u just have x+y=13/7
to find y, subract x from that side of the =, andput on the other. It would come out y=x+7 and 1/6
for the other one, the same... divide 3 into 15, get 5, end up with -x+5y=5. Take the -xto the other side, you get 5y=x+5, and to just get y, divide everything by 5, y=x/5+1

Answer 3

Solve for y just means to get y on one side of the equation all by itself.

7x + y = 13
y = 13 - 7x

3x + 5y = 15
5y = 15 - 3x
y = 3 - 3/5 x

Answer 4

problem #1 y= 13-7x

problem #2 5y=15-3x

If you need to solve for y, then you need to have y on one side of the =. So you like w/ question #1, you have to take away that 7x from that side, so you'll subtract it from each side. It will then look like 7x-7x+y=13-7x. On the right side the 7x-7x would cancel out. So you would have the answer of y=13-7x.

Answer 5

The problem people typically have with these equations is that they expect y to equal a number. In this case, it will not.

7x + y = 13
7x -7x + y = 13 - 7x
(Subtract 7x from both sides.)
y = 13 - 7x

Now, do the second one on your own. It's a little trickier, but the steps are the same as any two-step equation.

Answer 6

first of all I would isolate y in this equation

7x + y = 13
y=13-7x

then when you have that substitute it in to the second equation

3x +5y = 15
3x+5(13-7x)=15
3x+65-35x=15
-32x=-50
x=50/32
x=25/16

now you have X and you can substitute that in to either equation that you were given to get Y

7x+y=13
7(25/16)+y=13
175/16+y=13
y=13-175/16
y=208/16-175/16
y=33/16

Now if I did all my math correctly you you answer are

x=25/16 and y=33/16

Answer 7

take 1st equation and get y alone ....y=13-7x
then same for 2nd.......5y=15-3x...so y=3-(3x/5)

then since they are equal, make one equation

13-7x = 3 - (3x/5) since they both equal y


then solve

Answer 8

1. y=-7x+13

2. y=(-3x+15)/5