`a, 4 xx 342 xx 25`
`= ( 4 xx 25 ) xx 342`
`= 100 xx 342`
`= 34200`
`b, 48 xx 524 + 56 xx 524`
`= 524 xx ( 48 + 56 )`
`= 524 xx 104`
`= 524 xx ( 100 + 4 )`
`= 524 xx 100 + 524 xx 4`
`= 52400 + 2096`
`= 54496`
`c, 123 xx 486 - 22 xx 486 - 486`
`= 486 xx ( 123 - 22 - 1 )`
`= 486 xx 100`
`= 48600`
`d, 3/8 xx 7/8 + 7/8 xx 2/8 + 7/8 : 8/3`
`= 3/8 xx 7/8 + 7/8 xx 2/8 + 7/8 xx 3/8`
`= 7/8 xx ( 3/8 + 2/8 + 3/8 )`
`= 7/8 xx 1`
`= 7/8`
