8、In a class of 50 students, each student has either a triangle ruler or a straightedge, 28 students have a straightedge, among those who have a triangle ruler, 14 are boys, if it is known that there are 31 girls in the class, then the number of girls who have a straightedge is $\qquad$ people.
$$
\text { 8、 } 23
$$

Solution: The number of students who have a triangle ruler is $50-28=22$ (people), among which the number of girls is 22-14=8 (people). Therefore, the number of girls who have a straight ruler is $31-8=23$ (people).