To solve this equation, we need to first simplify the left side of the equation:

(1,2-х) + 1

= 1.2 - х + 1 (rearranging the terms)

= 2.2 - х

Now, we can set this equal to 1.8 and solve for х:

2.2 - х = 1.8

Subtract 2.2 from both sides:

2.2 - х - 2.2 = 1.8 - 2.2

-х = -0.4

Divide by -1 on both sides:

х = 0.4

Therefore, the solution to the equation (1,2-х) + 1 = 1.8 is х = 0.4.