D
given the 2 expressions, construct 2 equations
b + h = 34 → (1)
b - h = 8 → (2) with b > h
add (1) and (2) term by term to eliminate h
2b = 42 ⇒ b = 21
substitute b = 21 in (1) and solve for h
21 + h = 34 ⇒ h = 34 - 21 = 13
hence bh = 21 × 13 = 273 → D