Total marks of 15 students = 15 x 145 = 2175.
Average marks of 15 students (excluding two lowest scores) = 13 x (145 + 5) = 1950.
∴ Total of two lowest scores = 2175 1950 = 225
Given that two scores are consecutive multiples of 9 * 9x + 9x + 9 = 225 18x = 216
=> 18/x = 216 => x = 216/18
Lowest score = 9x = (216/18) x 9 = 108