Hi ! Thanks for the answer.
But my RCA tablet is "dead" and the seller replaced it be an -Acer 7", B1-770, with Android 5.0.1- Build Acer_AV0L0_B1-770_0.001.00_WW_GEN1. It's why I did not react to the given tips, sorry! :-X
How is it possible to Root this tablet. It's not done yet !
Thank you for the attention to my question.
Cilou