2 (−5.581 + 9.12 ) − (15.38 + 8.76 ) r A? z5.581+9.12b= B? 15.38+8.76b= n 3 (6.28 − 1.18 ) − (4.449 + 2.558 ) r A? 6.28p1.18b= B? 4.449+2.558b= n 4 (2.69 − 9.85 ) − (−6.88 − 5.82 ) r A? 2.69p9.85b= 6