Let A, B, C represent their weights. Then, we have: A + B + C = 45 × 3 = 135 ……(i) A + B = 40 × 2 = 80 …….(ii) B + C = 43 × 2 = 86 ……(iii) Adding Eq. (ii) and (iii), We have: A + 2B + C = 166 ……(iv) Subtracting Eq. (i) from (iv), we get: B = 31 Hence, B’s weight = 31 kg