let the number of marbles be as follows:
after the described action
box1 = x/3 (you took 2/3 away, so 1/3 remains)
box2 = 129-x-y + 15 = 144-x-y
box3 = 3y
then (x/3) : 144-x-y : 3y = 2:3:9
so then (x/3)/(144-x-y) = 2/3
3x + 2y = 288 (equ#1)
also (x/3)/3y = 2/9
x = 2y (equ#2) sub that into equ#1 to get
y = 36
then x = 72
box3 36 --- total 129
box1 = 24
box2 = 36
box3 = 108
24:36:108 = 2:3:9
After: 24:36:108 (total 168)
Before: 72:21:36 (total 129)
Method used: trial and error
Start with "after" combinations with the right ratios, determine the required operations and "before" compositions, and see which one adds up to 129 "after".
It only took three attempts.
simply just wat is says above 168
Math - There were 7 times as many marbles in Box A as in Box B. After Joyce ...
math - there were 7 times as many marbles in box a as in box b. after joyce ...
maths - Boxes A nad B contain a total of 480 marbles. After 0.25 of the marbles ...
HELPPPP - A box contains 2 white marbles, 3 blue marbles, 7 black marbles and 9 ...
math - A box contains 2 white marbles, 3 blue marbles, 7 black marbles and 9 ...
maths - Mr Tan had a box of marbles. 2/3 of the marbles were blue and the rest ...
math - in a jar of 40 marbles there are 12 red marbles 19 blue marbles and there...
statistics - A box of marbles contains an equal number of red marbles and yellow...
statistics - Suppose a box of marbles contains an equal number of red marbles ...
math - How do I approach this problem? Seven green marbles and three red marbles...