(me brushing my teeth) and (you going to school)
Notice this is a geometric progression since each number multiplied by some factor equals the next number in the sequence, in this case,

Then by applying the formula for sum to infinity of a geometric progression,
Answer:
31-3n
Step-by-step explanation:
d=-3
a1=28
an= 28+(n-1)(-3)=28-3n+3
an=31-3n
is there a table or something you can add because I cant tell anything with the information you gave.
See attachment file below.
Hope it helped!!