In the picture below, for the text underlined in red color: 7X(MOD 11) = 72(MOD 11) =49(MOD 11)
My questions are:
(1) obviously there is no equal relationship between 72(MOD 11) and 49 (MOD 11), and where does 49 come from?
(2) X and Y are picked up randomly, are 7 and 7 in 7X and 11 in MOD 11 also picked up randomly, or is it some algorithm？ there is no any explanation in the textbook I have
(3) in the text marked in blue color, where does 2401 come from?