Equation :
This parabola is facing downwards and highest point of the parabola is it's vertex.
Highest point is (-2,2)
so the vertex is (-2,2)
The graph is passing through (-1,0)
Equation in vertex form is


Substitute back in Equation

the graph has two x intercepts -1 and -3
that means (x+1) and (x+3) are the factors
multiply factors to get the equation in standard form

-2x^2-8x-6=0
I believe the problem ask for s which is the standard
deviation. We must recall that the formula for z statistic is stated as:
z = (x – x over bar) / s
Where,
z = z statistic = 2.5
x = sample value or sample score = 102
x over bar = the sample mean or sample average = 100
s = standard deviation = unknown
Rewriting the equation in terms of s:
s = (x – x over bar) / z
Substituting the given values into the equation:
s = (102 – 100) / 2.5
s = 0.8
Therefore the standard deviation s is 0.8
Equivealent= like
6/18, 5/15
3/9, 2/6