690十47X52一398脱式计算
=690+2444-398
=3134-398
=2736
98一18X5十170
=98-90+170
=8+170
=178
15X7十85X2
=105+170
=275
720÷36÷2
=20÷2
=10
690十47X52一398
=690+2444-398
=690+2046
=2736
98一18X5十170
=98-90+170
=8+170
=178
15X7十85X2
=105+170
=275
720÷36÷2
=720÷（36x2）
=720÷72
=10
解: 690十47X52一398
=690+47(50+2)-398
=690+2350+94-398
=3040+94-398
=3040-304
=2736
98一18X5十170
=98-90+170
=8+170
=178
15X7十85X2
=105+170
=275
720÷36÷2
=20÷2
=10
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