Aflagpole casts a shadow 10 ft long. if a man 6 ft tall casts a shadow 4ft long at the same time of day, how tall is the flagpole?

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.)