Question 1162993
Draw and label the triangle:
J,  point where is John
M, point where is Mary
T,  the tree on opposite bank
B,  point where directly accross river where tree is located
JM=428.3
x=JB
TB, the distance accross river


That forms a triangle JMT.
Interior angle at M is  64.55 degrees.



Question would then be asking for length TB.


{{{system(TB/x=tan(45.57),TB/(428.3-x)=tan(64.55))}}}
Solve the system to find TB.


A different method may be possible.