Answer:
a(n)=1800+(n-1)200
Step-by-step explanation
The usual formual is an=a1+d(n−1)
a1=The first number is the number you would start on
so 1800=a1
n=the number of times you would do it
you would usually put n-1 because the first number is already been put though the formula
d=the amount of change between each number
so 200=d
A(n)= a of n, like f(n) means f of n
so that why it is a(n)=1800+(n-1)200
i also got it right on A.pex