Explanation

This is a rational equation in one variable. Let x be the number subtracted from both terms: (27 - x)/(35 - x) = 2/3. Cross-multiplying: 3(27 - x) = 2(35 - x), i.e. 81 - 3x = 70 - 2x, so x = 11. Checking: (27 - 11)/(35 - 11) = 16/24 = 2/3, as required. Option (c) 9 is a near-miss from an arithmetic slip in cross-multiplication. Hence option (d).