Question 233219
let the boxes be a, b, c, d


a = b/3
b = c/3
c = d/3


this means that:


d = 3*c
d = 3*b
b = 3*a
a = a


you have a + b  + c + d = 80


replace d with 3*c to get:


a + b + c + 3*c = 80


replace c with 3*b to get:


a + b + 3*b + 3*3*b = 80


replace b with 3*a to get:


a + 3*a + 3*3*a + 3*3*3*a = 80


simplify and combine like terms to get:


a + 3*a + 9*a + 27*a = 80 which becomes:


40*a = 80 which becomes:


a = 2


you get:


a = 2
b = 3*2 = 6
c = 3*3*2 = 18
d = 3*3*3*2 = 54


your answers are:


a = 2
b = 6
c = 18
d = 54