From all single digit we need digit whose square (B*B) give same single digit i.e.B; hence we can have 1, 5 and 6 in hand.
equation: (AAB)*B=CB5B
B=1; (AA1)*1= always give same no. i.e. (AA1)
B=5; (AA5)*5= we can not have second last digit 5, (5*any single digit=either 5 or 0 at unit place)
B=6; (AA6)*6=C656, we need A either 2 or 7 so we can have 5 at second place.
A=7

(776)*6=4656

couldnot understand the question