adults = a
children = c
total passengers = t
ratio :
4c = 22 a
c = (22 a) / 4
a + c = t
a + c = 91
a + (22 a) / 4 = 91
for all of the elements, we multiply by 4, so it's much easier formula.
4a + 22a = (91 * 4)
26a = 364
a = 364 / 26 = 14
c = (22 a) / 4
c = (14 * 22) / 4 = 77
