Répondre :
D: -3y=15. -> -3y/3=15/3. -> -y=5. -> y=-5
E: 18a=15a2. -> 18a/a=15a2/a. -> 18=15a. -> 18/3=15a/3. -> 6=5a. -> a=6/5
E: 18a=15a2. -> 18a/a=15a2/a. -> 18=15a. -> 18/3=15a/3. -> 6=5a. -> a=6/5