1) 2,6*{5,8+6,25*[9,3-3,1*(8,76-2*2,88)]}=2,6*{5,8+6,25*[9,3-3,1*(8,76-5,76)]}=2,6*[5,8+6,25*(9,3-3,1*3)]=2,6*[5,8+6,25*(9,3-9,3)]=2,6*(5,8+6,25*0)=2,6*5,8=15,08.
2) [1,2+3,2*(3X+0,75)]:3=3,6 <=> 1,2+3,2*(3X+0,75)=10,8 <=> 3,2*(3X+0,75)=9,6 <=> 3X+0,75=3 <=> 3X=2,25 => X=0,75.
3) 2X+0,72=4,28 <=> 2X=3,56 => X=1,78.