total = x
x - (1/4)x = (3/4)x
(1/3) * (3/4)x = (3/12)x = (1/4)x [por simplificación]
(3/4) - (1/4) = 1/2
(1/6) * (1/2)x = (1/12)x
(1/2) - (1/12) = (6/12) - (1/12) = (5/12)x
(5/12)x = 30
Para despejar X:
(5/12)x = 30
x = 30 / (5/12)
x = (30 * 12) / 5
x = 360 / 5
x = 72
Mi escrito tiene 72 folios.
Espero te haya ayudado.
Saludos.