Log5(7+5x)=log5(7-x)+2
log5(7+5x)=log5(7-x)+2
log5(7+5x) - log5(7-x) = 2
log5( (7+5x)/(7-x) ) = 2
5² = (7+5x)/(7-x)
25(7-x) = (7+5x)
175 - 25х = 7 + 5х
30х = 168
х = 168/30 = 5,6