1. Total number of lines if no three points are collinear: The number of ways to choose 2 points out of 15 to form a line is given by the combination formula: \[ \binom{15}{2} = \frac{15 \times 14}{2} = 105 \] 2. Adjust for the collinear points: Since 5 points are collinear, they all lie on a single line. Normally, these 5 points would contribute \(\binom{5}{2} = 10\) lines. However, since they are collinear, they only contribute 1 line instead of 10. 3. Calculate the adjusted total number of lines: Subtract the overcounted lines and add the single line for the collinear points: \[ \text{Total lines} = \binom{15}{2} - \binom{5}{2} + 1 = 105 - 10 + 1 = 96 \] Therefore, the total number of straight lines formed is: \(\boxed{96}\)