32 + 33 à détailler svp urgent

33)
a) 7x + 11 = 4x + 15
3x = 4
x = 4/3

b) 9x - 2 = 2x - 7
7x = -5
x = -5/7

c) -3 = x - 5
2 = x

d) 5 - 7x = -3x + 2
-4x = -3
-x = -3/4
x = 3/4

a) 3a - a - 11 =15
2a = 15
a = 15/2 = 7.5

b) 2 = 4b -3b -5
  2 = b -5
7 = b

c)  -3 = 5a +a -15
    -3 = 6a -15
-3+15 = 6a
12 = 6a
12/6 = a 
2 = a

d) (je simplifie un peu les détail parce que c ets long)
7x +3x = 5+2
10 x = 7
x = 7/10

e) 5x - 3x = 6-6 
 2x = 0
x = 0/2 = 0

f) 3x -3x = 7+5
0 = 12 impossible