`a) 12347 + 23455 + 76545`
`= 12347 + ( 23455 + 76545 )`
`= 12347 + 100 000`
`= 112347`
`b) 123 xx 4 xx 25`
`= 123 xx ( 4 xx 25 )`
`= 123 xx 100`
`= 12300`
`c) 2 xx 4 xx 25 xx 50`
`= ( 2 xx 50 ) xx ( 4 xx 25 )`
`= 100 xx 100`
`= 10000`
`d) ( 450 xx 27 ) : 50`
`= 450 xx 27 : 50`
`= ( 450 : 50 ) xx 27`
`= 9 xx 27 = 243`