6×5-1/2x=18
-0.5x=18-30
-0.5x=-12
x=24
3/4x-1/3x=5/2
5/12x=5/2
x=6
x-6/13x=2/5
7/13x=2/5
x=26/35
x＋5/7x=8/9×3/2
12/7x=4/3
x=7/9
祝你学习愉快