Question 192912
heading  is  angle  from  true  north.

sketch  a  rough  triangle,  start  at  right  angle  on  right  side,  west  is  horizontal  line  left, hypotenuse  is  20 deg  from  north  from  left  position .  The  required  distance  in  along  vertical  line  from  initial  position  to  intersection  with  hypotenuse. 

The  20  deg  angle  is  also  the  vertex  angle  at  top  of  triangle,  by  AIA.

in  short,  tan  20 deg  =  30 /x

x=30/tan20=82.424.