if NR+RN=ABC where A,B,C,N and R are digits what is maximum value of B+C?

Answer 1

99+99 = 198
B+C = 17

The only way you could get more than that would be if the number ended in 99.
But NR+RN = 11(R+N) so R+N would have to end in 99. I think you can see why that cannot be so.

Answer 2

78
+87
-----------
165

N= 7
R=8
A=1
B=6
C=5

B+C=11