a) x + 6 = 4
x =4 - 6
x = -2
b) -2 = x + 5
-2 - 5 = x
x = -7
c) 5x + 11 = 21
5x = 21 - 11
5x = 10 /:5
x = 2
d) 8c -9 + 4c -5 + 2c = 7
8c + 4c + 2c = 7 + 9 + 5
14c = 21 /: 14
c = 21/14
c = 3/2
e) 5 + 2y = 17
2y = 17 - 5
2y = 12 /:2
y = 6
f) 3a + 2a = 19 + 4 - 3
5a = 20 /: 5
a = 4
g) 5b - b = 13 - 5 + 10
4b = 18 /:4
b = 18/4
b = 9/2
h) 5d - d = -8 + 11
4d = 3 /: 4
d = 3/4