aide s'il vouplai 5ème maths

Bonjour
p = 5 x ( a +9)
p = 5a + 45

l = 2 x ( a - 4)
l = 2a -  8

a = 3 x ( 10 +b)
a = 30 + 3b

t = (11 +c) x 7
t = 77 + 7c

e = (d + 8a +b) x 8
e = 8d + 64a + 8b

u = 5 x (6 -b)
u = 30 - 5b

n = (9.3 - c ) x 7
n = 65.1 - 7c

A = 3a + 15
B = 14 + 6b
c = 32 + 4b +4c
D = 5a - 20 +10y

s = (d - 2g + 3c) x 10
s = 10d - 20g + 30c

a) P= 5*(a+9)
  = 5*a +5*9
  = 5a +45

A= 3*(10+b)
  = 3*10 +3*b
  = 30 +3b

T= (11+c)*7
  = 7*11 +7*c
  = 77 +7c

E= (d+8a+b)*8
  = 8*d +8*8a +8*b
  = 8d +64a +8b

L= 2*(a-4)
  = 2*a -2*4
  = 2a -8

U= 5*(6-b)
  = 5*6 -5*b
  = 30 -5b

N= (9,3-c)*7
  = 7*9,3 -7*c
  = 65,1 -7c

S= (d-2g+3c)*10
  = 10*d -10*2g +10*3c
  = 10d -20g +30c

b) A= 3*(a+5)
       = 3a +15

B= 2*(7+3b)
  = 14 +6b

C= 4*(8+b+c)
   = 32 +4b +4c

D= (a-4+2y)*5
  = 5a -20 +10y