Bonjour,
2) 1/4 = 4c/3 - 2/5
1/4 +2/5 = 4c/3
5/20 + 8/20 = 4c/ 3
13/20 = 4c/3
(13*3)/20 = 4c
39/20 = 4c
(39/20 / 4 = C
39/ (20*4) =c
39/ 80 = c
3) 2d - 5(d-3) = -3(d-5)
2d -5d+15 = -3d+15
-3d +15 =-3d+15
-3d+3d = 15-15
0=0
d= 0
4) 5e+8/3 = 12e+1/2
8/3 -1/2 = 12e -5e
16/6 -3/6 = 7e
13/6 = 7e
e= (13/6 )/7
e= 13/(6*7)
e=13/ 42