I don't get where u got the 1:80 from 2:20 the time left in math class? Why and how did u change 2:20 to 1:80? I'm 25 yrs out of school trying to help my 5th grade daughter
just as you cannot subtract 7 from 2 in
32 - 17
you change 32 to 20+12
Now you can borrow the 7 from 12, leaving 15
2 hrs 2 minutes is the same as 1 hr 80 minutes. Now you can subtract from a number bigger than 20.