Think of it like this: you need to rearrange things so y is by itself on one side of the equation:
xy-8=k
First add 8 to both sides to get rid of the 8 on the y side:
xy-8+8=k+8
xy=k+8
Divide both sides by x to get y by itself:
(xy)/x=(k+8)/x
y=(k+8)/x
That's it. Just remember that you always add or subtract before multiplying or dividing.
We cannot answer since you didn't give any numbers at all to solve this with.
-y + y equals 0.
k = x y x = k/y
For y - 2y - 3y equals 0, y equals 0.
x = y/k: 24 = 6/k so k = ¼; when y = 8, x = 8/¼ = 32
b = y - mx.
y= -2x
y - 3 = 0 y = 3
y = x/k so k = 1/25; when x = 1, x/k, hence y, = 25
y / r2 = a constant (k) so k = 405/81 ie 5. k = y/4 when r = 2, so y = 20.
y = x/k so 15 = 6/k making k = 0.4. when x = 10 y = 10/0.4 ie 25 alternatively y/x = k ie 15/6 = k so k = 2.5; y/10 = 2.5 making y = 25.
y=x+4