To find the value that should be inserted into each rectangle, we need to first determine the total number of parts represented by the ratio of tickets sold to unsold tickets.
The ratio of tickets sold to unsold tickets is 5:3, which means there are a total of \(5 + 3 = 8\) parts.
Since the baseball team has 1,200 tickets to sell, we can find the value for each part by dividing the total number of tickets by the total number of parts:
\[ \text{Value of each rectangle} = \frac{1200 \text{ tickets}}{8 \text{ parts}} = 150 \text{ tickets} \]
Therefore, the number 150 should be inserted into each rectangle.