Bonjour tout le monde qui pourrais m'aider svp merci d'avance

Bonsoir !

A = 5/4+3/2 = > Dc = 4

A = 5/4 + 3x2/2x2 = 5/4+4/4 = 11/4

B = 1/3-10/21 = > Dc = 21

B = 1x7/3x7 - 10/21 = 7/21-10/21 = -1/7

C = 1/3+4/5 => Dc = 15

C = 1x5/3x5 + 4x3/5x3 = 5/15+12/15

C = 17/15

D = 8+2/5 = > Dc = 8x5/1x5+2/5

D = 40/5+2/5 = 42/5

E = 8/7-2 = > Dc = 7

E = 8/7 - 2x7/1x7 = 8/7-24/7 = -6/7

F = -13/3-2/7 = > Dc = 21

F = -13x7/3x7 - 2x3/7x3 = -91/21-6/21

F = -91/21-6/21 = -97/21

Dc = dénominateur commun

Bonne soirée.