To determine the profit from sales if the price of the t-shirts is $15 each using the function \( p(x) = -2(x - 9)^2 + 100 \), we need to substitute \( x = 15 \) into the function.
- Substitute \( x = 15 \) into the function:
\[ p(15) = -2(15 - 9)^2 + 100 \]
- Calculate \( 15 - 9 \):
\[ 15 - 9 = 6 \]
- Now calculate \( (6)^2 \):
\[ 6^2 = 36 \]
- Substitute \( 36 \) back into the equation:
\[ p(15) = -2(36) + 100 \]
- Calculate \( -2(36) \):
\[ -2(36) = -72 \]
- Now add \( 100 \):
\[ p(15) = -72 + 100 = 28 \]
Thus, the profit from sales when the t-shirts are priced at $15 each is \( \boxed{28} \).