(Contributed by Mrs Chin-Toh)
My solution:
Men : Total
1u : 3u
-3 +3
--------------
1 : 4
I would multiply the whole branch of "Men" by 4 to match with the branch of "Total":
4u - 12 = 3u + 3
Manipulating the "u" to LHS and numbers to RHS:
4u - 3u = 3 + 12
1u = 15
Assumption: there are only men and women in the bus, no children!
(a) number of women at first, 2u --> 2x15 = 30
(b) Altogether, 3u --> 3x15 = 45
