In order to write an expression that relates the siblings heights we need to attribute variables to each brother. First we will call Martina's height as "m", then we can call her little brother's height as "b". The problem states that Martina's height is 3 inches less than twice the height of her brother so we have:
m = 2*b - 3
Then the problem gives us the height of her brother that is 28 inches tall, so b = 28. We can now compute Martina's height:
