Answer: 3 (first choice)
A power to a power gives a multiplication of powers, e.g.,
(7¹⁰)² = 7²⁰
So the left side is 7²⁰ / 7⁴ and we divide the top and bottom by 7 get we
(7¹⁰)² / 7⁴ = 7²⁰ / 7⁴ = 7¹⁹ / 7³
We compare that to the right side 7¹⁹ / 7ˣ and it's clear x=3.