Answer:
[tex] \boxed{\sf -(x+y)} [/tex]
Step-by-step explanation:
[tex] \sf Simplify \: the \: following: \\ \sf \implies (3x - 4y) - (4x - 3y) \\ \\ \sf - (4x - 3y) = - 4x + 3y: \\ \sf \implies 3x - 4y + \boxed{ \sf - 4x + 3y} \\ \\ \sf Grouping \: like \: terms, 3x - 4y - 4x + 3y = \\ \sf (3y - 4y) + (3x - 4x) : \\ \sf \implies(3y - 4y) + (3x - 4x) \\ \\ \sf 3y - 4y = - y : \\ \sf \implies \boxed{ - y} + (3x - 4x) \\ \\ \sf 3x - 4x = - x : \\ \sf \implies \boxed{ - x} - y \\ \\ \sf \implies - (x + y)[/tex]
