Exercice 1 : ecrire a et b sous la forme d'une fraction la plus simplifiée possible

Bonsoir , 
A = 1 - (2/3 + 1/4 ) 
A = 1 - (8/12 + 3/12)
A = 1 - 11/12
A = 12/12 - 11/12
A = 1/12
B = (3 - 5/2 ) / (1 + 1/5 )
B = (6/2- 5/2) / (5/5 + 1/5 ) 
B = (1/2) / (6/5)
B = 1/2 × 5/6
B = 5/12

A= 1-(8+3/12)= 1-(11/12)= (12/12)-(11/12)=1/12

B=(6-5/2)/(5+1/5)= (1/2)/(6/5)= (1/2)×(5/6)=5/12