How to calculate the height of an object using trigonometry

In the 30-60-90 triangle below side s has a length of and side r has a length

Problem melissa is her dad build a walkway in their backyard. the walkway will be 54 feet long and 1.5 feet wide. the local hardware store sells tiles which are 1.5 by 1.5 feet and come in boxes of 12. how many boxes of tiles do they need?

This is different from the first one can someone me