The LCM of two prime numbers a and b (a>b) is 391, then 3b – 2a is divisible by

Correct Answer: (A) 5

Since $a$ and $b$ are prime numbers with $a > b$, their LCM is simply their product: $a$$\times$ b = 391. Factoring 391 into primes gives $391 = 23$$\times$ 17, so $a = 23$ and $b = 17$. Evaluating $3b - 2a$ yields $3(17) - 2(23) = 51 - 46 = 5$.