Question 1204848
This is a typical exercise coming up from time to time.  Many like it have been solved by now.


Use description to draw and label the diagram.
If x is point A to shed bottom
and 
y is how tall the shed, then



{{{system(y/x=tan(20),y/(x+30)=tan(12))}}}

 and now solve.  You want to finish with numerical value for y.