Завдання 1402 - 1500 » 1439 (7-12)

7) 12 – 5(х + 1) = 7 + Зх – 2х; 12 – 5х – 5 = 7 + х; –5х – х = 7 – 7; –6х = 0; х = 0. 8) –0,2(3 – у) + 1,2 = –0,2(у – 1) –0,6 + 0,2у + 1,2 = –0,2у + 0,2; 0,2y + 0,2y = 0,2 – 0,6 ; 0,4y = –0,4; y = –1. 9) 1 – 4z – 3(1 – z) = –5(z + 2); 1 – 4z – 3 + Зz = –5z – 10; –z + 5z = –10 + 2; 4z = –8; z = –2. 10) (18 – х) – 7(2х – 4) = 5х + 20; 18 – х – 14х + 28 = 5х + 20; –15 х – 5х = 20 – 46; –20х = –26; х = 1,3. 11) 3(0,4y + 3) – 0,6y = 8; 1,2у + 9 – 0,6у = 8; 0,6y = 8 – 9 ; 0,6y = – 1; y = –12/3. 12) 2(2+х) + (4х –1) ∙ 3 = 10х – 7; 4 + 2х + 12х – 3 = 10х – 7; 14х – 10х = –7 – 1; 4х = –8; х = –2.