I need help :’) with math: Which equation matches this table?

X 1 2 3 7 8
Y 6 12 18 42 48

1.y = x - 6
2.y = x ÷ 6
3.y = 6 x
4.y = x + 6

an = 15 (1/5)^(n-1)

Step-by-step explanation:

In a geometric series, each term is multiplied by a common ratio to get the next term.  Such that:

an = a₁ (r)^(n-1)

Here, the first term, a₁, is 15.  The common ratio, r, is 1/5, because each term is divided by 5 to get the next term.  So:

an = 15 (1/5)^(n-1)

Your answer is correct, well done!