Question 51086
Solving for y simply means that you must get the y on one side of the equals sign by itself using the standard rules of algebra.

1) 5x-y = 10  Here, you would first add y to both sides of the equation.
5x = 10+y  Then you subtract 10 from both sides.
5x-10 = y  Many teachers like to see the dependent variable (y in this case) on the left side, so rewrite this as:
y = 5x-10...and there you have it.

2) x+4y = -8 In this one, you would subtract x from both sides.
4y = -x-8 then you divide both sides by 4.
y = -(1/4)x - 2

Do you see the idea here? You want to rewrite each equation so that it's in the form...y = something. Let's do one more:

0.1x + 0.5y = 3.5 Here, you need to get rid of the decimals in a way that leaves you with integral (whole number) numbers of y. You can do this by multiplying everything by 2.
(2)0.1x + (2)0.5y = (2)3.5 Simplify this.
0.2x + y = 7 Now subtract 0.2x from both sides.
y = -0.2x + 7

Ok now try the others on your own.
If you are still having trouble with it, repost.