1. Let

be the number of seats in the

-th row. The number seats in the

-th row relative to the number of seats in the

-th row is given by the recursive rule

Since

, we have





So the explicit rule for the sequence

is

In the 15th row, the number of seats is

2. Let

be the amount of profit in the

-th year. If the profits increase by 6% each year, we would have





with

.
The second part of the question is somewhat vague - are we supposed to find the profits in the 20th year alone? the total profits in the first 20 years? I'll assume the first case, in which we would have a profit of

3. Now let

denote the number of pushups done in the

-th week. Since

,

, and

, it looks like we can expect the number of pushups to quadruple per week. So,

starting with

.
We can apply the same reason as in (2) to find the explicit rule for the sequence, which you'd find to be