1,6,8 are figures composed of straight as well as curved lines

3,7,9 are closed figures shaded by oblique line segments

2,4,5 are figures composed of straight lines only.

The second figure is obtained from the first figure by moving the line segment to the opposite side of the square boundary and replacing it with two similar line segments. Also, the element in the lower-left corner gets replaced by two similar elements - one placed in the upper-left and the other placed in the lower-right corner.

The simplest rectangles are AEHG, EFJH, FBKJ, JKCL and GILD i.e 5 in number.

The rectangles composed of two components each are AFJG and FBCL i.e 2 in number

Only one rectangle namely AFLD is composed of three components and only one rectangle namely ABCD is composed of five components.

Thus, there are 5 + 2 + 1 + 1 = 9 rectangles in the given figure.

Given are the two AP'S:

15,12,9.... in which a=15, d=-3.............(1) 

-15,-13,-11..... in which a'=-15 ,d'=2.....(2)

now using the nth term's formula,we get

a+(n-1)d = a'+(n-1)d'

substituting the value obtained in eq. 1 and 2,

15+(n-1) x (-3) = -15+(n-1) x 2

=> 15 - 3n + 3 = -15 + 2n - 2

=> 12 - 3n = -17 + 2n

=> 12+17 = 2n+3n

=> 29=5n

=> n= 29/5

Take a look at the below sereies :

1500 - 25 = 1475

1475 - 27 = 1448

1448 - 29 = 1419

1419 - 31 = 1388

1388 - 33 = 1355

1355 - 35 = 1320

It clearly shows 1389 is Wrong Number

The number of points of intersection of 37 lines is C237. But 13 straight lines out of the given 37 straight lines pass through the same point A.

Therefore instead of getting C213 points, we get only one point A. Similarly 11 straight lines out of the given 37 straight lines intersect at point B. Therefore instead of getting C211 points, we get only one point B.

 Hence the number of intersection points of the lines is C237-C213-C211 +2 = 535

It means that the first half of the alphabet is interchanged with second half of the alphabet. After making changes, nth letter from the left will be (n + 13)th letter of original series, ie English alphabet; If n is less than 14. But if n is more than 13, nth letter from left will be (n - 13)th letter from left.
In the given equation, we have to find out (13 - 7 =) 6th letter from right => (26 - 6 + 1 =) 21st letter from the left. Hence, required letter's position is more than 13; therefore the required letter is (21 - 13 =) 8th letter from left of original series, ie H.