Q.1
If you want to convert 124 [8] into base 10 (the [8] means a subscript 8)

Q.2
If you want to convert 124 [8] into base 10 (the [8] means a subscript 8)

Q.3
If you want to convert 217 into base 8

Q.4
If you want to convert 217 into base 8,