There are x parallel straight lines.

(9*8)/2-[x(x- 1)]/2=24

The subtracted [x(x- 1)]/2 is unreasonable. The reason ~ your setting is not clear. X straight lines are parallel to each other, including many situations, such as

1、

X bars are all parallel to each other;

2、

Two of them are parallel to each other, and the other x-2 is parallel to each other, but the two sets of parallel lines intersect.

In these two cases, the deduction points are different ~

These are all your mistakes ~ ~ According to your algorithm, you can use (9 * 8)/2-24.

= 12, and then calculate how to subtract 12 points.

Provide an answer, four parallel horizontal lines, then draw four vertical lines intersecting them, and the last line crosses these eight lines diagonally ~ ~