-3 + 7*(2.5x - 7.6) = -3.66 + 2.1x

Expand the left side:

-3 + 17.5x - 53.2 = -3.66 + 2.1x

Combine like terms:

17.5x - 56.2 = -3.66 + 2.1x

Now, isolate the variable x:

Subtract 2.1x from both sides:

17.5x - 2.1x - 56.2 = -3.66

15.4x - 56.2 = -3.66

Add 56.2 to both sides:

15.4x = 52.54

Divide by 15.4 to solve for x:

x = 3.41

Therefore, the solution to the equation is x = 3.41.