pouvez vous m'aider a cet exercice si dessus merci.

1) Multiple commun de 15 et 20 : 60.
13/15 = 13*4/15*4 = 52/60
11/20 = 11*3/20*3 = 33/60

2) a. 13/15 - 11/20 = 52/60 - 33/60 = 19/60
b. 13/15 + 11/20 = 52/60 + 33/60 = 85/60 = 5*17/5*12 = 5/12

Bonsoir,

1. On a :
13/15=(4×13)/(4×15)=52/60.
11/20=(3×11)/(3×20)=33/60.

2.
__a. 13/15 - 11/20 = 52/60 - 33/60 = (52-33)/60 = 19/60.
__b. 13/15 + 11/20 = 52/60 + 33/60 = (52+33)/60 = 85/60.

:)