If n is a positive integer, what is the tens digit of n ?
(1) The hundreds digit of 10n is 6.
Multiplication by 10 will shift all digits one to the left. Ten's digit of n must be 6.
n=4324324242468<- 6 in tens place
10n=43243242424680<-hundred's digit in 6 because 0 occupied the units place and rest all of digits moved 1 to the left.
n=69<-6 in tens place
10n=690<-6 in hundreds place
(2) The tens digit of n + 1 is 7.
n+1=70<-tens digit of n+1 is 7 when tens place of n=6
n+1=74<-tens digit of n+1 is 7 when tens place of n=7