This is a puzzling one! The answer is indeed -3/4 but I was unable to prove it using mathematics appropriate to the "middle school" level. Sorry I couldn't be more helpful.
(To prove it I generated the first few terms of its Laurent series, a Calculus topic. The first few terms are -(3/4) + (41/64x) + and as x approaches minus infinity the term with "x" in the denominator goes to zero, leaving the constant value -3/4 as the answer. )
