answer is 9
75 previous number is 37 so 37*2+1=75
37 previous number is 19 so,19*2-1=37
assume 19 previous number is x:
19 previousnumber is x so x*2+1
by substitute the given options in x
1.10*2+1=21(is not the next number)
2.9*2+1==19(is the next number)
3.3*2+1=7
4.8*2+1=17
so the option 2 is correct bcz x of next number is 19