31,8-(1/7+4/7 x)=1 2/3 x+4,8
31,8 - (1/7 + 4/7х) = 1 2/3х + 4,8 31 8/10 - 1/7 - 4/7х = 1 2/3х + 4 8/10 31 8/10 - 1/7 - 4 8/10 = 1 2/3х + 4/7х 318/10 - 1/7 - 48/10 = 5/3х + 4/7х (2226-10-336)/70 = (35+12)/21х 1880/70 = 47/21х 47/21х = 188/7 х = 188/7 : 47/21 = 188/7 * 21/47 = 12
спасибо