4 ×1.8+19.2× 4 7 7 3 × 2 + 3 ×0.6 4 54 15 21 × 3 4 + 10 21 × 3 4 - 3 4 9 10 17 ÷13 9 +10 × 4 17 3.7× 6 5 5 +1.3÷6