In the following number-pairs, the second number is obtained by applying certain mathematical operations to the first number. Select the set in which the numbers are related in the same way as are the numbers of the following sets.
(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)
50, 4
80, 7​

50, 4
80, 7​
Logic: (2nd number + 1) × 10 = 1st number

(4 + 1) × 10 = 50 

(7 + 1) × 10 = 80 

Now let's check each option:

Option A: 90, 11
(11 + 1) × 10 = 120 ≠ 90 

Option B: 70, 6
(6 + 1) × 10 = 70 
This matches perfectly!

Option C: 100, 11
(11 + 1) × 10 = 120 ≠ 100 

Option D: 60, 6
(6 + 1) × 10 = 70 ≠ 60 

Thus, correct option is (b).