Help writing an equation to solve

Question

What is the equation to solve this problem? Fiona finds1shell on her first day at the beach. Every day that week she finds twice as many as she did the day before. How many shells did Fiona find on
the seventh day?

Answer 1

You could make a list for the number of shells found each day.  Remember the number of shells doubles each day.

 

Day 1 = 1 shell

Day 2 = 2 shells

Day 3 = 4 shells

Day 4 = 8 shells

Day 5 = 16 shells

Day 6 = 32 shells

Day 7 = 64 shells

Answer 2

y=total number of shells found on a particular day

y=2^(x-1) where x=the number of the day

y=2^(7-1)=2^6

y=64 shells

1:1, 2:2, 3:4, 4:8, 5:16, 6:32, 7:64