What’s 8/6 - 1/8 need it in a fraction

You paint a 1/2 of a wall in 1/4 hour. how long will it take you to paint one wall

I’ve been trying all day to figure this puzzle out. i need the work for it aswell. it is a factoring polynomials tarsia. the image is below.

Describe how to determine the average rate of change between x = 4 and x = 6 for the function f(x) = 2x^3 + 4. include the average rate of change in your answer.