Chapter 8 - Systems of Linear Equations and Problem Solving - 8.3 Solving Applications: Systems of Two Equations - 8.3 Exercise Set - Page 527: 15

23 classic watches and 12 plus watches.

We first write the word problem as an equation. Next, we solve the equation using substitution. Doing this, we find: $$ x+y=35, 39.99x+59.99y=1639.65 \\ \frac{3999}{100}\left(35-y\right)+\frac{5999}{100}y=\frac{8198}{5} \\ y=12 \\ x=35-12=23 $$