5 x 5 equels 10
1 straight line. An infinite number of curved lines.
There are 91 lines.
Only one line can be drawn through eight points.
1
An infinite number of lines can be drawn through a single point, but only one through two points (of course, if the points don't have the same coordinates).
15 lines.
3 lines and one plane
One.
Through any two distinct points, exactly one line can be drawn. For 5 non-collinear points, each pair of points can form a line. The number of ways to choose 2 points from 5 is given by the combination formula ( \binom{5}{2} ), which equals 10. Therefore, 10 lines can be drawn through 5 non-collinear points.
In Euclidian or plane geometry, there can be only one line through two fixed points. Lines cannot actually be drawn; if you see it it is not a geometric line. If the points are on a curved surface as in a geometry that is non-Euclidian, then there can be infinitely many lines connecting two points.
If you're talking about straight lines (not curves) the answer is one.
A line consists of infinitely many points which all satisfy some condition. In that respect, one point or even a trillion points do not make a line. There are infinitely many lines that can be drawn through one point.