3(х-1)+(х-2)-х = 3x -3+x-2-x = 3x-5
5n-3(n+2)+(n-6) = 5n - 3n -6 +n - 6 = 3n - 12 = 3 (n - 4)
m-(2m-6)+3(m-3) = m - 2m + 6 + 3m - 9 = 2m - 3
2(3x+1)-(x-2)-3x = 6x + 2 - x + 2 - 3x = 2x + 4 = 2 ( x+2)
через 240 секунд_________________