Explanation: Its actually simple logic, generally we think to find out the relation between the opposite sides, but here the relation is in between adjacent numbers, which is very unusual though.

9 * 2 = 18 -1 = 17

160 *2 = 320 -1 = 319

475 * 2 = 950 – 1 = 949

To solve this, replace a n digit number by adding all digits, and solve, keep on repeating it until you get single digit.

10×11×12={(1+0)×(1+1)×(1+2)}^2 =6^2=36=3+6=9

11×12×13={(1+1)×(1+2)×(1+3)}^2 =24^2 =(2+4)^2=36=3+6=9

12×13×14={(1+2)×(1+3)×(1+4)}^2 =60^2 =(6+0)^2 =36 =3+6=9

13×14×15={(1+3)×(1+4)×(1+5)}^2 =120^2 =(1+2+0)^2 =9

14×16×20={(1+4)×(1+6)(2+0)}^2 =70^2 =(7+0)^2 =49 =4+9=13=1+3=4

2-1=2×2+(2/2)x(2/2)-2×1=3
8-5=8×8+(8/2)x(8/2)-8×5=40
4-4=4×4+(4/2)x(4/2)-4×4=4
thus
10-10=10×10+(10/2)x(10/2)-10×10=25