If there are x boys, there are 2x girls. boys+girls=27 gives x+2x=27. Solving, 3x=27 or x=9. Since there are 2x girls, there are 2*9=19 girls.
Step-by-step explanation:
I guess we only need to add 2 hours and 38 minutes to the depart times to get arrival, and deduct 2 hours and 38 minutes from arrival to get departure.
a) 05 00 -> 07 38
b) 07 20 -> 09 58
c) 08 40 -> 11 18
d) 10 58 -> 13 36
e) 15 45 -> 18 23
f) 18 22 -> 21 00
g) 18 39 -> 21 17
h) 20 47 -> 23 25
3)
(x/3)+(2/5)
(5x/15)+(6/15)
(5x+6)/15
4)
(2/x)+(3/7)
(14/7x)+(3x/7x)
(3x+14)/(7x)
5)
(x/2)+(1/3)+(x/4)
(6x/12)+(4/12)+(3x/12)
(9x+4)/12