Idk how to change 15% into a mixed number in simplest form

In simplified exponential notation, the expression a^2•a^-3•a 1/a 0

Sole with work in 10 years, the average number of hours of tv watched per week by teenagers dropped from 23.9 to 21.4. find the percent of change.

Acircle has a radius of 5/6 units and is centered at (3.6, 7.8) write the equation of this circle