In order to get h alone, you must eliminate the 40. So to do this, you must subtract the 40 (as you always do the opposite operation, and if there isn't one, it is always positive), and this becomes 55h=150.
To find out what h is, you then divide both sides by 55. 55h/55=h
150/55= 2.727
Therefore, h=2.727
HOpe this helps :)
