Eric did not do his math. He is in the doghouse now. Tonight he did 20 math problems. Ten of them were for today. Ten of them were for yesterday. He started on them 5:41 p.m. He finished at 7:09 p.m. How long did it take Eric to do the math?
7:09 - 5:41 = (7 - 5) : (9 - 41)
= 2 : (-32)
= 1 : (60 - 32)
= 1 : 28
1 hour 28 minutes
