55.7—(1.8—4.3)=55.7+4.3-1.8=60-1.8=58.2
55.7-1.8+4.3=55.7+4.3-1.8=60-1.8=58.2
原式=55.7-1.8+4.3=55.7+4.3-1.8=60-1.8=58.2
