determine the extreme values of objective function f=9x+7y subject to 7≥x+2y, 6≥x-y, 0≥x,0≥y by lpp method

Astick 2 m long is placed vertically at point b. the top of the stick is in line with the top of a tree as seen from point a, which is 3 m from the stick and 30 m from the tree. how tall is the tree?

0if x and y vary inversely and y=6 as x=7, what is the constant of variation?

How can constraints be used to model a real-world situation?