Answer: The answer is (n = 5r + 10).
Step-by-step explanation: Given that in a theatre, there are 15 seats in the first row, 20 seats in the second row, 25 seats in the third row, etc.
We are to write the linear equation that represents the number of seats 'n' in each row 'r'.
Now,
Number of seats in the 1st row = 15 = 5 × 3 = 5 × (1+2),
number of seats in the 2nd row = 20 = 5 × 4 = 5 × (2+2),
number of seats in the 3rd row = 25 = 5 × 5 = 5 × (3+2), etc...
Therefore, number of seats 'n' in the r-th row is given by the following linear equation -
n = 5 × (r+2), i.e., n = 5r + 10.
Thus, the required linear equation is n = 5r + 10.