What have you tried so far?
You will want the boom to miss the top of the roof. It is 10+ (1/2)(8)= 14 m behind the truck. The roof is 9 m wide and has a "pitch of 9/12" so is (9)(9/12)= 27/4= 7.75 m high which means the peak of the roof is 6+ 7.75= 13.75 m above the ground. The boom starts 2.5 m above the ground so the peak of the house is 13.75- 2.5= 11.25 m above the base of the boom. But the hot tub itself is 1 m high so we will need 11.25+ 1= 12.25 m clearance. A right triangle with height 12.25 m and base 14 m has .