pouvez vous m'aider pour cet exercice svp ?

a = 3a-b-c
= 3(2/3) -(-3/2) -(-3/4)
= 2 +3/2 +3/4
=8/4+6/4+3/4
=17/5

b=  -2a+4b-5c
b =-2(2/3) +4(-3/2) -5(-3/4)
b = -4/3 -12/2 +15/4
b = -14/12 -72/12 +45/12
b = - 86/12 +45/12
b =-41/12

c = 6b² -3a+5
c = 6(-3/2) -3(2/3) +5
c = 6(9/4) -2+5
c = 27/2+3
c =27/2 +6/2
c =33/2

d = 1/a +1/b +1/c
d = 1/2/3 +1/ -3/2 + 1/-3/4
d = 3/2 -2/3-4/3
d = 9/6 -4/6-8/6
d = 9/6-12/6
d = -3/6
d = -1/2

e = a+c / a-b
e = 2/3 -3/4  / 2/3 +3/2
e = 8/12 -9/12  / 4/6+9/6
e = -1/12  / 13/6
e = -1/12 x 6/13
e = -6 /156
e = -1/26