Since all triangles in these questions are similar, we use that the ratios of corresponding sides are equal
(1)
=
=

solving
=
( cross-multiply )
5x = 36 ( divide both sides by 5 )
x =

solving
=

4y = 30 ⇒ y =

(2)
let h be the height of the flagpole, then
=

4h = 275 ⇒ h = 68.75 feet
(3)
=

12.75x = 561 ⇒ x = 44 feet