(x- 1/5) :16/19= 3 1/6 :13 1/3

(x-1/5) : 16/19 = 3 1/6 : 13 1/3;
(x-1/5) : 16/19 =19/6 : 3/36;
(x-1/5) : 16/19 =16/6 * 3/36;
(x-1/5) : 16/19 =19/2 * 1/36;
x-1/5 = 19/2 * 1/36 * 16/19;
x-1/5 = 1/2 * 1/36 * 16/1;
x-1/5 =  1/2 * 1/9 * 4/1;
x-1/5 = 4/18;
x = 1/5 + 4/18;
x = 18/90 + 20/90;
x = 38/90;
x = 19/45.

Удачи :)