2.3 - [1.89 - {3.6 - (2.7 -  (0.8-0.03) ̅)}]

Using BODMAS rule, we have

2.3 – [1.89 – {3.6 – (2.7 – 0.77)}]

= 2.3 – [1.89 – {3.6 – 1.93}]

= 2.3 – [1.89 – 1.67]

= 2.3 – 0.22

= 2.08