Answer:
1 unit. If unit is cm, it is 1cm^3.. If unit is meter it will be 1m^3
See photo for drawing.
Words:
Suppose a square is 100%,
50%: the square is divided into two equal parts, and one of them is shaded, therefore it is 50%.
25%: the square is divided into 4 equal parts, and one of them is shaded, therefore it is 25%.
150%: there are two squares, each divided into 2 equal parts, and 3 of them is shadowed, therefore it is 150%.
You set it up as a y=mx+b problem 150=55x+40 then you subtract 40 from 150 making 110=55x so x=2