Start at 125 create a pattern. that. subtracts. 6 from each number

125-6n where n is an integer
we start at n=0, wait, we want to start at n=1 because first term, not zeroeth term

so
125-6(n-1) or
125+6-6n or
131-6n is da equation
make a patter
f(x)=131-6n
where the domain is all natural numbers (1,2,3,4,5, etc)
first term is f(1)=125