Question 40864
(2x*x)/(2x+x)=8 or 2x~2/3x=8 or 2x~2=24x or 2x~2-24x=0 or 2x(x-12)=0 or x=12 thus 2*12 or 24 min for the slower maching.

proof 2*12*12/(2*12+12)=8 or 288/36=8 or 8=8