Answer:
100
Step-by-step explanation:
it is a bit unclear to me, what that problem description means.
if I understand it correctly, than z is directly depending on x².
so, z = 16 for x = 2. x² = 4
I pondered a little bit, as there are several possibilities to connect 16 with 4 as a driving factor (e.g. 2⁴ = 16, 4×4 = 16, 12 + 4 = 16).
I decided to go with the simplest interpretation with the usual meaning of "varies" (multiplication) : 4×x²
that would mean
z = 4×x² = 4×5² = 4×25 = 100
