The answere is 213 boxes
If you add 3 dozens to 14 dozens of boxes of envilopes , then you get 17 dozens of boxes of envilopes.Then of you sum up the 1/2 (2/4 ) with the 1/4.You get 3/4. Finally, you add 17 dozens to 3/4 of a dozen you get 17 3/4 dozens( wich is 213 boxes )
The formula of the area of a triangle:

b - the bash - the height
We have:
b - the base3b - the height486 - the area
Substitute:
Answer: The length of the height is equal 54 units.
Where’s the figure or nets?
Find the area of one side, which is length x width:
2/3 x 2/3 = 4/9 square ft.
There are 6 sides to the prism, so multiply the area of one side by 6:
4/9 x 6 = 24/9 = 2 6/9 = 2 2/3 square ft.