The country which shares longest border with

Select the number that can replace the question mark (?) in the following series. 17, 21, 30, 46, 71, ?

Some equations are solved on the basis of a certain system. Find the correct answer for the unsolved equation on that basis.

If 2 is subtracted from the second digits of each of the numbers, how many numbers thus formed will be divisible by three?

Four number-pairs have been given, out of which three are alike in some manner and one is different. Select the number-pair that is different.

If all the digits of each number are added, the sum of which number will be the largest?

12 5 20

m 13 8

If ‘m’ is the resultant of the first row, what the resultant of the second row?

Select the number-pair that is different from the other three.