Yo someone help me, i dont understand this

1/3 of 60 min = 20 min
1/4 of 60 min = 15 min

20 min + 15 min = 35 min
60 min - 35 min = 25 min left over for reading

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.