They carried 3 10-lb bags.
Giovanni's bag was 5/6 full, so 1/6 of that bag was used.
Frances' bag was 2/5 full, so 3/5 of that bag was used.
The dad's bag was 3/4 full, so 1/4 of that bag was used.
Soil put in first flower bed was
1/6 * 10 + 3/5 * 10 + 1/4 * 10 =
= (1/6 + 3/5 + 1/4) * 10
= (10/60 + 36/60 + 15/60) * 10
= 61/60 * 10
= (1 1/60) * 10
= 10 10/60
= 10 1/6
Answer: The put in 10 1/6 lb of soil.