Hello there!
We first would have to determine how many feet are in each brick of the 4 bricks.
(6/4)= 1.5
There are 1.5 for ever brick.
Now that we know this, we do 1.5 by how many bricks we would want to multiply by, which in this case is 20.
(1.5x20) = 30 ft.
Your correct answer would be . . . 30 ft tall.
I hope this helps you!