Beginning Algebra
No; A contains an extra b-term outside the parentheses, which makes it different from B for most values
Yes, but only when a and b are integers; otherwise, algebraic manipulation is invalid
Yes; after distributing the 2 and combining like terms, A simplifies to 2a + 5b, which equals B
They are equivalent only if b = 0, because only then does the outside 3b not affect the sum