The correct option is D 18
Given that after adding 4 to the result we get the number 40 we get the equation as,
x+4=40
∴x+4=40
x=36
The Factors of 36 are
1,2,3,4,6,9,12,18 and 36 itself.
Now we take a pair of numbers from the factors of 36, which when added gives us the number in the options and when multiplied gives us the result 36.
A. 12 = 6×6=36
B. 13 = 4×9=36
C. 15 = 3×12=36
D. 18 = No pair matches.
E. 20 = 2×18=36
Hence option D is the correct answer.