Following the rule of PEDMAS
1/2 - 1/3 xx 1/4 + 1/5 1/6 div 1/6
1/5 1/6 = 1/5 cdot 1/6 since there is no symbol attached!
Hence;
1/2 - 1/3 xx 1/4 + 1/5 cdot 1/6 div 1/6
1/2 - 1/3 xx 1/4 + 1/5 xx 1/6 div 1/6
So we'll take it step wise..
Since there are Parenthesis, Exponents.. we'll go to;
Division
1/2 - 1/3 xx 1/4 + 1/5 xx color(red)(1/6 div 1/6)
1/2 - 1/3 xx 1/4 + 1/5 xx (color(red)(1/6 xx 6/1)) -> "Transposed!"
1/2 - 1/3 xx 1/4 + 1/5 xx color(red)(1/cancel6 xx cancel6/1)
1/2 - 1/3 xx 1/4 + 1/5 xx 1/1
Multiplication
1/2 - color(blue)(1/3 xx 1/4) + color(blue)(1/5 xx 1/1)
1/2 - 1/12 + 1/5
Addition
1/2 - color(orange)(1/12 + 1/5)
Note, Addition and Subtraction deals with finding the LCM..
LCM of 12 and 5 = 60
1/2 - color(orange)((5 + 12)/60)
1/2 - 17/60
Subtraction
color(green)(1/2 - 17/60)
LCM of 2 and 60 = 60
color(green)((30 - 17)/60)
13/60