I don’t know the answer but I can tell you how to do it subtract starting value minus final value divide that amount by the absolute value of the starting value multiply by 100 to get percent decrease if the percentage is negative it means there was an increase not a decrease
It’s function one cause if you find the slope on the table it’s 3/1 which is basically just 3. Then the y-intercept is -3.
Function 1 slope is 5 or 5/1 and y-intercept is 4
The decimal is 0.6 to find the decimal form you take 9÷15 = 0.6