[tex]3x - 5 = 10 = > 3x = 10 + 5 = > 3x = 15 = > x = \frac{15}{3} = 5 \\ 7x + 80 = 10 = > 7x = 10 - 80 = > 7x = - 70 = > x = \frac{ - 70}{7} = - 10 \\ 3(x + 4) = 15 = > 3x + 12 = 15 = > 3x = 15 - 12 = > 3x = 3 = > x = \frac{3}{3} = 1 \\ 7(8 - x) = 2(x - 2) = > 56 - 7x = 2x + 4 = > - 7x - 2x = 4 - 56 = > - 9x = - 52 = > x = \frac{52}{9} [/tex]