Question 1037056
Draw this diagram of two triangles.
s, distance from base point of bird to Susan;
m, distance from base point of bird to Mark;
s+m=7.
h, how high the bird from the base point.
Angle measure at s is 20 degrees;
Angle measure at m is 50 degrees.


Two more equations are {{{system(s/h=cos(20),m/h=cos(50))}}}.


You really have a system of these equations:
{{{system(s+m=7,s/h=cos(20),m/h=cos(50))}}}.
You can solve this system for all three unknown variables.  The question asks for the value of h.