Решите уравнение:
а) (x + 2) + x = 9;
б) x + (7 + x) = 11;
в) x + 2x − 5 = 40;
г) x + (x + 4) + x = 16;
д) (x + 5) + (x + 6) = 21;
е) 2(x − 8) = 20.
(x + 2) + x = 9
2x + 2 = 9
2x = 9 − 2
2x = 7
x = 7 : 2
x = 3,5
x + (7 + x) = 11
2x + 7 = 11
2x = 11 − 7
2x = 4
x = 4 : 2
x = 2
x + 2x − 5 = 40
3x = 40 + 5
3x = 45
x = 45 : 3
x = 15
x + (x + 4) + x = 16
3x + 4 = 16
3x = 16 − 4
3x = 12
x = 12 : 3
x = 4
(x + 5) + (x + 6) = 21
2x + 11 = 21
2x = 21 − 11
2x = 10
x = 10 : 2
x = 5
2(x − 8) = 20
2x − 16 = 20
2x = 20 + 16
2x = 36
x = 36 : 2
x = 18
