Greetings from Brasil...
Here's our problem:

From potentiation properties:
Mᵃ ÷ Mᵇ = Mᵃ⁻ᵇ
division of power of the same base: I repeat the base and subtract the exponents
So, in our problem
= 12³ ÷ 12⁷
12³ ÷ 12⁴ = 12³⁻⁷
12⁻⁴
We also know about another property: P⁻ⁿ = (1/Pⁿ) so
12⁻⁴ = (1/12⁴)