3*（2/15+1/12）-2/5
=3* 2/15 + 3* 1/12 -2/5
=2/5 + 1/4 - 2/5
=1/4
（1-75％）×（1＋4分之1）
=（1- 3/4）*（1+ 1/4）
=1/4 * 5/4
=5/16
0.25×31分之75＋31分之49×25％
=1/4 *（75/31 + 49/31）
=1/4 * 4
=1
（4.6×6.38＋3.62×4.6）＋9.2
=4.6*(6.38+3.62)+9.2
=4.6*10+9.2
=46+9.2
=55.2
28.8-640％-2.8-4.6
=28.8-2.8-(6.4+4.6)
=26-11
=15
9分之2×4分之3＋0.75×9分之7-75％
=2/9 * 3/4 + 3/4 * 7/9 -3/4
=3/4 * (2/9 + 7/9 -1)
=0
19-12％x＝7
0.12x=12
x=100
4分之3x-5％＝175％
3/4 x=1.75+0.05
3/4 x=1.8
3/4 x=9/5
x=9/5 * 4/3
x=12/5