Always remember the formula:

y = mx + c

Where m is the slope or gradient. And c is the y-intercept

------------------------------------------------------------

1. y = 1/3x + 4 [Here we only needed to insert the values]

-------------------------------------------------------------

2. Ok, this one is a little more tricky because we have to solve for the c-value.

So: y = 3x + c

But they give us the point (1 ; -2)

So insert that into the x and y values.

Then -2 = 3(1) + c

and c = -5

Thus y = 3x - 5

----------------------------------------

3. Now we have no values. Only points.

But you know that m = (y2-y1)/(x2-x1)

So then m = (4 - 2)/(-2 - 3)

Thus m = 2/-5

Now we once again have to solve for c like in the 2nd problem.

So insert one of the given points into the equation.

then 2 = (2/-5)(3) + c

So c = 5,6

Thus y = (2/-5)x + 5,6

Hmm, thats a weird value...

Anyway i hope this helps