Rewrite the equation: 5y=10x-8 and divide by 5: y=2x-8/5. The slope of the line is 2, and the slope of the line we need to find is also 2, because parallel lines have the same slope.
We know that the slope of the line we have to find is 2. We can write y=2x+c where we have to find c. Substitute the coords of the given point: x=2, y=4:
4=4+c, so c=0 and the equation of the line is simply y=2x.