а) \(67.9+81.7=149.6\); б) \(65.04+1.8=66.84\); в) \(77+5.8=82.8\); г) \(31.834+40.97=72.804\); д) \(5.59+3.26=8.85\); е) \(80.049+27.951=108\).
Ответ: 149.6; 66.84; 82.8; 72.804; 8.85; 108.