To solve this equation, we need to simplify both sides and isolate the variable у.

Starting with the left side of the equation:
1/3у - 4/3у - 3 = 2 1/2
1/3у - 4/3у - 3 = 5/2
(-3/3у) - (4/3у) - 3 = 5/2
-7/3у - 3 = 5/2

Next, we need to add 3 to both sides to isolate у:
-7/3y = 5/2 + 3
-7/3y = 11/2

Now, to solve for y:
y = (11/2) / (-7/3)
y = (11/2) * (-3/7)
y = -33 / 14

Therefore, the solution to the equation is у = -33/14.