We can simplify the expression 1/2x - 1 by finding a common denominator for the two terms and combining them:
1/2x - 1 = 1/2x - 2/2
= (1/2)x - 1
So, the expression equivalent to 1/2x - 1 is (A) 1/3(3/2x - 1).
We can verify this by distributing the 1/3 to the expression inside the parentheses:
1/3(3/2x - 1) = (1/3)(3/2x) - (1/3)(1)
= (1/2)x - 1/3
This is equivalent to the original expression (1/2)x - 1, so the answer is (A) 1/3(3/2x - 1).