Which answer is the explicit rule for the sequence: 10.5, 9, 7.5, 6, 4.5, 3,

an=12−1.5n

an=11−1.5n

an=12.5−1.5n

an=12+1.5n

The common difference of the terms in the sequence
d = 9 - 10.5 = 7.5 - 9 = 6 - 7.5 = -1.5

The first term of the sequence is 10.5.
Therefore, the equation that represents the sequence is
an = 10.5 - 1.5(n -1)
Expanding
an = 10.5 - 1.5n + 1.5
Simplifying
an = 12 - 1.5n

The answer is THE FIRST OPTION.