va rog cate puteti dintre astea 3

a)(15x-6-6x)/4=1=>9x-6=4=>9x=10=>x=10/9
b)18x-12+5=17x-2=>x=-2+7=>x=5
c)21/9x+7/6=6/9x+7/3=>21/9x-6/9x=7/3-7/6=>15/9x=7/6=>90x=63=>x=63/90=>x=7/10