3.5у + 0.8 = 5.5у - (1.2у + 0.8) - 2.4

First, distribute the negative sign inside the parentheses:

3.5у + 0.8 = 5.5у - 1.2у - 0.8 - 2.4

Combine like terms on the right side:

3.5у + 0.8 = 4.3у - 3.2

Next, move all the terms involving у to one side by subtracting 4.3у from both sides:

3.5у - 4.3у + 0.8 = -3.2

Simplify:

-0.8у + 0.8 = -3.2

Subtract 0.8 from both sides:

-0.8у = -4

Now divide by -0.8 to solve for у:

у = 5

Therefore, у = 5.