For every equation, we have to choose a value for x, and solve for y.
For part a) we have that the equation is:

If we choose the following value for x:

And substitute it in the equation, we find the value of y:

Answer for part a) when x=1, the value of y is y=6/7
For part b) we have the equation:

If we choose the following value for x:

and substitute it in the equation to find y:

To solve for y, first, we solve the multiplication between 5 and 3:

Now we subtract 15 to both sides:

Finally, divide both sides by 3:

Answer for part b) when x=3, the value of y is y=-2
For part c) we have the equation:

In this case, we can choose a value for x in such a way that we eliminate the fraction. For this, we can again choose the value:

And we substitute it:

1/3 by 3 is equal to 1:

Next, combine the like terms on the left side 5-1 which is 4:

And finally, subtract 4 to both sides:

Answer for part c) when x=3, the value of y is y=3