Question 520
you need to convert these equations to form y=...

3x+15y=24 converts to y=-(3/15)*x+24/15
3x-8y =24 converts to y=(3/8)*x-24/8

You can now plot these curves by plotting opints and drawing a straight line:

{{{graph( 300, 300, -5, 5, -5, 5, -(3/15)*x+24/15, (3/8)*x-24/8) }}}