Y=(3/5)x -3 and 5y =3x-10 these lines are and the second question?

Look at the first line:  y = (3/5)x - 3.  What happens if you multiply each term by 5, to eliminate the fraction?

5y = 3x - 3

Compare this to the second equation, 

5y - 3x = -10, or 5y = 3x - 10.

The coefficients of x and y (as 3 and 5 here) determine the slope of a straight line.  Since 5y = 3x is present in both equations, the two lines MUST be parallel.

y = 4
4y = 6   =>   y = 6/4

y+4 and y =3/2 are both horizontal lines.  Since they are horiz., they are parallel.