It is like cross multiplication, which is the actually height over the height it casts .
which is. 6ft. / 4ft. = x / 10ft.
x is the unknown height the flagpole and 10ft is the height of the shadow.
You then cross multiple .
Which will give you
4ft.x = 10ft. × 6ft.
which will give you
4ft.x = 60ft.
so you switched the place of the 4ft. to the oppose side, it will give you ÷4ft.
It is ÷ because 4ft. has a variable which is x ( can also so be any letter, but I used x instead).
you are now left with
x = 60ft. ÷ 4ft.
x = 15ft.
( 15 because 60 ÷ 4 is 15 and ft because you are asked to find how tall the flagpole is in ft.)
