From this situation we can write a system of equations if we tag the orange buttons with , the yellow buttons with , the green buttons with and the blue buttons with :
There were 820 orange buttons:
(1) Number of orange buttons
The number of orange buttons was 160 fewer than the number of yellow buttons:
(2)
The number of orange buttons was 210 more than the number of green buttons:
(3)
1/3 of the total number of buttons in the container were blue buttons:
If the total is the sum of the buttons of each color, we have:
(4)
At this point we have our system with 4 equations and 4 unknowns.