98.3, 94.1, 89.9, 85. is what sequence

If you mean Arithmetic or Geometric it is: I believe it is Arithmetic.

Hmm, it might be aritmetic
so
89.3-94.1=4.2
94.1-89.9=4.2
so it is an aritmetic sequence with common differnce of -4.2

an=a1+d(n-1)
a1=first term
d=common differnce
n=which term
an=nth tem

so
the equation is
an=98.3-4.2(n-1) or
an=102.5-4.2n