How do you solve this: f^-1(3) when f(x)=2x-7/3

The given dot plot represents the average daily temperatures, in degrees fahrenheit, recorded in a town during the first 15 days of september. if the dot plot is converted to a box plot, the first quartile would be drawn at __ , and the third quartile would be drawn at link to the chart is here

What is the upper quartile in the box plot?

Find the solution of this system of equation -7x+y=-20 9x-3y=36