assuming that the tank is empty
1 and 1/4 times what=3 and 1/2
convert to improper
1 and 1/4=1+1/4=4/4+1/4=5/4
3 and 1/2=3+1/2=6/2+1/2=7/2
5/4 times what=7/2
times both sides by 4/5 to clear fraction (5/4 timers 4/5=20/20=1)
what=28/10
what=20/10+8/10
what=2+4/5
answer is 2 and 4/5 hour or 2hr and 48mins