Число делится на 3 если сумма цифр в нем делится на 3, или:
Х(1/3+1/2)=6 2/3
х*(2+3)/6=20/3
х=20/3:5/6
х=8
5целых1/4х-2целых2/3х=1целая5/12
5ц1*3/4*3х - 2ц2*4/3*4х=1ц5/12
5ц3/12х - 2ц 8/12х=1ц5/12
4ц15/12х - 2ц8/12х=1ц5/12
2ц7/12х=1ц5/12
х=1ц5/12 : 2ц7/12
х=17/12 : 31/12
х=17/12 * 12/31
х=204/372
х=17/31
проверка
5целых1/4х-2целых2/3х=1целая5/12
(5ц1/4 * 17/31) -( 2ц 2/3 *17/31)=1ц5/12
(21/4×<span>17/31</span>=<span>21*17 / 4*31</span>=<span>357/124</span><span>) - (</span>8/3×<span>17/31</span>=<span>8*17 / 3*31</span>=<span>136/93)=1ц5/12
</span>2ц109/124 - 1ц43/93=1ц5/12
<span>(357/124</span>−<span>136/93</span>=<span>3*357/3*124 </span>−<span>4*136/4*93</span>=<span>1071/372</span>−<span>544/372</span>=<span>1071−544/372</span>=<span>527/372</span>=<span>сократим на 31</span>=<span>17/12)</span>=1ц<span>5/12
1ц5/12=1ц5/12</span>