21 – 3(4х – 2,1) = 13 – 6х
21-3(4х-2,1)=13-6х 21-12х+6,3=13-6х -12х+6х=13-21-6,3 -6х=-14,3 х=-14,3:(-6) х=2 цел 23/60
21-12x+6,3=13-6x 6x=14,3 x≈2,38