2a
33
+ b9
____
99
If a and b represent positive single digits in the correctly worked computation above, what is the value of a + 3b ?  Select:
A) 2
B) 7
C) 9
D) 11
E) 12

Rationale: adding the digits in unit ' s place , a + 3 + 9 = 19 ( since a and b are positive single digits ) = > a = 7 now adding the digits in ten ' s place , 2 + 3 + b + 1 = 9 ( 1 has been carried over from nit ' s place addition ) = > b = 3 a + 3 b = 2 + 2 * 3 = 11 answer d
Answer: D