X:25=1/200
X=1/200×25
X=1/8
3/8+5/8×3/10
=3/8+3/8×5/10
=3/8×(1+5/10)
=3/8×3/2
=9/16
12÷(1/3+1/4)
=12÷7/12
=144/7
=20又4/7
45÷1.8+1.3×0.6
=25+0.78
=25.78
2/9×0.375÷6/7
=2/9×3/8×7/6
=7/72
X:25=1/200
X=1/200×25
X=1/8
3/8+5/8×3/10
=3/8+3/8×5/10
=3/8×(1+5/10)
=3/8×3/2
=9/16
12÷(1/3+1/4)
=12÷7/12
=144/7
=20又4/7
45÷1.8+1.3×0.6
=25+0.78
=25.78
2/9×0.375÷6/7
=2/9×3/8×7/6
=7/72