Could you please help me with this one?

Simplify the following:
13/5-6×11/20

-6×11  =  -66:
13/5+-66/20

The gcd of -66 and 20 is 2, so (-66)/20 = (2 (-33))/(2×10) = 2/2×(-33)/10 = (-33)/10:
13/5+(-33)/10

Put 13/5-(33)/10 over the common denominator 10. 13/5-(33)/10  =  (2×13)/10-(33)/10:
(2×13)/10-(33)/10

2×13  =  26:
26/10-(33)/10

26/10-33/10  =  (26-33)/10:
(26-33)/10

26-33  =  -(33-26):
-(33-26)/10

 
Answer: |  (-7)/10

I think you might mean this :

[13 + 1/5 ]  -  [ 6 +11/20 ]

Note that 13 + 1/5 =    66/5    and     6 + 11/20  =  131/20     ......   get a common denominator of 20

264 / 20  -  131/20   =

133 / 20   = 

6 + 13/20