Question 767565
We can assume points on the x and y axes to contain base and height.  
y/x=2/1 because we want height to be two times base.  We then have some unknown equation with obviously slope -2 to fit {{{y=-2x+b}}}.


The line must contain point (1, 8), so we make 8=-2*1+b,
b=8+2
b=10.

Our line must be {{{highlight(y=-2x+10)}}}


This can be checked if desired.  The x-intercept is at 0=-2*x+10, x=5.
Good, because height/base is 10/5=2 as we were specified to have.