[tex]5x+20y=10\implies y=\dfrac12-\dfrac x4[/tex]
is a line with slope [tex]-\dfrac14[/tex]. Any line parallel to it will have the same slope. Using the point-slope formula, the equation of the parallel line passing through (8, 3) is
[tex]y-3=-\dfrac14(x-8)\implies y+\dfrac13x=5\implies x+3y=15[/tex]
