Bonjour aide moi svp c est l exercice 1 a et b

A =7/18-5/12
18=3x6
12=2x6 ( PGCD = 2x3x6)
A=7x2/18x2 - 5x3/12x3= 14/36-15/36=-1/36
B = (2+3/4)/2-3/4)=(2x4/4 +3/4)/(2x4/4-3/4) = (8/4+3/4)/(8/4-3/4)=
(11/4)/(5/4)= 11/4x4/5 on simplifie par 4 = 11/5