51.one-sixth of a number is 3 less than one-half of the same number. What is the number?

53.the denominator of a fraction is 4 more than the numerator. If 4 is added to the numerator and 7 is
added to the denominator, the value of the fraction is 1/2, Find the original fraction.

69, aris can paint a room in 5 1/2hours. His brother can do the same job in 7 1/2 hours. How long will it take
them to paint the room together?

79.a boat travels 28 km upstream in 7 hours. It travels 48 km downstream in 4 hours. Find the speed of
the boat and the speed of the stream.