what is the graph of y-(-3)=-1/2(x-(0))

Yo know that it is a straight line, right? It's the point-slope form.

geez. just get rid of the parentheses:

y+3 = -x/2
y = -x/2 - 3

That's in slope-intercept form, so it should be easy to do.

Or, you can write it as

x+2y = -6

Now, set x or y equal to zero to find the intercepts. Draw a line through the two intercepts.