Looks like 14.4 because you have to add them all together and divide by the total numbers
(20+22+10+5+15)/ 5
For functions, there is only many input values, but there can be only one output value, and there can be no identical x values. For this, x=3.2. If y= 2*3.2 - 1, then y=5.4.
Just jump the gun and multiply -7 and the value of d
-2[7x^2-24]-31
I got
-14x^2+17
as the total answer btw...