Let's start by converting the fraction 3/4 into its decimal form, 0.75.
We can figure out how many pieces of wood that are 0.75 yards long can be cut from a two-yard plank this way:
2 / 0.75 = 2 (remainder 0.5)
Libby can cut two pieces of the desired length from the two-yard long plank of wood. She will have 0.5 yard leftover.