I can’t see the picture I’m sorry if I can’t help you
A/3=7/10
21=10a
a=2.1
100a=100*2.1=210
-4 x 8= -32+3=-29. -29/8= -3.625
In order to calculate the z-score of a normal distribution, you need to apply the formula:
z = (o - m) / s
where:
o = observed value
m = mean
s = standard deviation
In your case:
z = (259 - 239) / 25 = 0.8
The answer is, indeed, z = 0.8
