Each sheet of paper in Darren's notebook is 24.25 centimeters tall and has a margin at the top that is 2.5 centimeters tall. If there are 30 equal size lines on each page, how tall is each line?

I assume that there is no margin at the bottom because only the top one is mentioned. If so, then we have 24.25 - 2.5 cm space for 30 equal lines, what can be written as:

(24.25 - 2.5) / 30 =

= 21.75 / 30 =

= 0.725 cm

Answer: One line is 0,725 cm tall (or 7.25 mm)