What is an increasing or decreasing interval of a parabola? is it like the vertex or turning point of the parabola? i don't remember. : (

Well first, an interval is a set of real numbers, usually x values. For example 0 ≤ x ≤ 1 is an interval. If the y values for the x values of the set increase as the x values increase, then the interval is increasing. If the y values for the x values of the set decrease as the x values increase, then the interval is decreasing. I hope that wasn't confusing, if you have questions, ask.

20 percentage, you can also do it on a calculator.

How much is 32 out of 40 written as a percentage? convert fraction (ratio) 32 / 40 answer:   80%