Answer:
14
Step-by-step explanation:
Geometric mean = nth root (product of individual values of set of data)
from the question, n=2,
product of individual values of set of data= 2/5*490 = 196
Therefore Sqrt (196) =14
NB: As n is 2, we use sqrt, if n is 3, we use cube root and so on
Tia is correct because she used PEMDAS
16 - 8 ÷ 8
= 16 - 1
= 15
Therefore, Tia is correct & the answer is 15
-AaronWiseIsBae
A is

absolute value is always positive, the minus sign vanishes (it literally means "how far away from zero" something is. distance can't be negative.)
B ist just 18