18 would have to be the mean because of the average
check the picture below.
now, if we split that triangle like so with that red line, we can use the right-triangle there, to get θ.

Lets take this step by step.
1-4-x-(4-1)=-x-2-(4)
first, we'll simplify the parentheses on the left side of the equation.
1-4-x-3=-x-2-(4)
second, we'll combine like terms on the left side.
-6-x=-x-2-(4)
third, we'll combine like terms on the right side of the equation.
-6-x=-6-x
since these are equal, (x=x), we have infinitely many solutions.
There’s no work for you to show
Answer:
x²+4=0
Step-by-step explanation:
x²=-4
√x² = √-4
x = 2i
x is an imaginary number