Given,
The straight lines l1 and l2 pass through the origin and trisect the line segment of the line L:9x+5y=45 between the axes,
And m1 and m2 are the slopes of the lines l1 and l2,
Now on plotting the diagram we get,

Given equation of line, L:9x+5y=45
⇒5x+9y=1
Now using the section formula between point A(5,0)&B(0,9) we get the value of point C&D
⇒C≡(310,3) and D≡(35,6)
Now finding the slope {m}_{1}&{m}_{2} we get,
{m}_{1}=\frac{3-0}{\frac{10}{3}-0}=\frac{9}{10}&{m}_{2}=\frac{6\times 3}{5}=\frac{18}{5}
So, equation of line y=(m1+m2)x will be,
y=(109+1036)x=29x
So, intersection point with L will be,
7y=45⇒y=745,x=710
Hence, y−x=745−10=5