To be parallel lines both must have the same slope. Our reference line is:
y=0.8x-3 so the slope is 0.8, given the point (5,0) we can solve for the y-intercept, or "b" of y=mx+b for our parallel line.
0=0.8(5)+b
0=4+b
b=-4 so
y=0.8x-4 is the parallel line to y=0.8x-3 that passes through (5,0)