a) (5x-(7x-2a))+7x = 5x - 7x + 2a + 7x = 2a + 5x;
б) 11x+(12y-3x)-(4x+3y) = 11х + 12у - 3х - 4х - 3у = 4х + 9у
a) (5x-(7x-2a))+7x = 5x - 7x + 2a + 7x = 2a + 5x;
б) 11x+(12y-3x)-(4x+3y) = 11х + 12у - 3х - 4х - 3у = 4х + 9у