1/2 +(2/3 / 3/4) +(4/5 x 5/6)=

1/2 +(2/3 / 3/4) +(4/5 x 5/6)=

1/2 + (2/3 * 4/3) + 20/30
1/2 + 8/9 + 20/30
1/2 + 8/9 + 2/3

Change them to fractions with a common denominator and add the numerators.

(2/3)/(3/4) = (2/3)x(4/3) = 8/9

(Are you sure you did not mean (2/3) x (3/4), which is 1/2 ?

(4/5)x(5/6) = 4/6 = 2/3

The common denominator will be 18.
9/18 + 16/18 + 12/18 = 37/18