Answer:
third box
first box
second box
Step-by-step explanation:
1/3x + 1/4 -2/3x; combine like terms
-1/3x + 1/4 (third box)
1/3x + 1/4 + 2/3x; combine like terms
(3/3)x +1/4 (first box)
3/3 is 1, so we don't have to write it
2/3 + 3/4x -1/3; combine like terms
1/3 + 3/4x (swap, and is second box)
