Explanation:

A=1.5B
A/B=3/2(efficiency ratio)
A/B=2/3(ratio of day)
(3–2)=1=8(according to question)
A takes =8×2=16 days
B takes=8×3=24 days
they together take(1/16+1/24)=5/48
as they work alternate days so (5/48×9)=45/48
therefore 9×2 days=18 daymust take
remaining work is (1–45/48)=3/48
as atfirst A start the work
so 1/16=1day
so 3/48=(16×3/48)=1 day
therefore totl days are 18+1=19