[tex] \frac{18 : 6 . 2 + 20 : 5}{10 - 4 . 3} [/tex]

(18:6.2 + 20:5)/(10-4.3)
First do the divided and the times first become
(3.2 + 4)/(10-12)
(6+4)/(10-12)
Second do the sum and the minus become
(10)/(-2)
And last do the fraction become
(-5)
So the answer is (-5)