how high is a tree that casts a 30ft shodow at the same time a 12ft pole casts a shodow which is 6ft long

h/30 = 12/6

h = 60

or, since the tree's shadow is 5 times as long as the pole's, the tree is 5 times as tall as the pole. 5*12=60 That is,

h/12 = 30/6