Answer: Equation to solve the problem :

There was 243 customers on 5th day .
Explanation:
Given: The number of customers at a new taco truck triples every day for a week. the function
represents the number of customers on day x.
Substitute f(x) =243 in the given equation , we get

Also, we know that


The bases are same it implies the exponents must be equal.

Hence, There was 243 customers on 5th day .