28/67×(10 11/13-2 11/13÷ 1/2)÷3 1/2
= 28/67 × (139/13 - 27/13 ÷ 1/2) ÷ 7/2
= 28/67 × (139/13 - 27/13 × 2) ÷ 7/2
= 28/67 × (139/13 - 54/13) ÷ 7/2
= 28/67 × 85/13 ÷ 7/2
= 28/67 × 85/13 × 2/7
= (28 × 85 × 2) / (67 × 13 × 7)
= 4760 / 6151
≈ 0.7743