What is 0.8 continued as a fraction

How do you solve a question like this?

Find the volume of the solid whose base is the region bounded by f(x), g(x) and the x-axis on the interval [0, 1], and whose cross-sections perpendicular to the y-axis are squares. your work must show the integral, but you may use your calculator to evaluate it. give 3 decimal places for your answe

Factor the polynomial by its greatest common monomial factor.