Well, 2 2/3 is 2 hrs and 40 mins, and he needs that exact amount to have 7 hrs. So, 7hrs-2 2/3hrs = 4 1/3hrs (4 hours and ten minutes.)
Answer:
Step-by-step explanation:
1/3x+2/3x-2/3x: x equasion
3/4+(-1/4)
1/3x + 2/4(or 1/2)
1/3x+1/2
(note that positive 2/3 and -2/3 cancel out)