To combine like terms in the expression (7x + 3y - 2 + 6x - 1 - y), first, group the terms with (x), (y), and the constant. Combine the (x) terms: (7x + 6x = 13x), the (y) terms: (3y - y = 2y), and the constants: (-2 - 1 = -3). The simplified expression is (13x + 2y - 3).