`a, 675 + 125 + 723 - 23`
`= ( 675 + 125 ) + ( 723 - 23 )`
`= 800 + 700`
`= 1500`
`b, 325 . 40 + 325 . 60 - 25 . 100`
`= 325 . ( 40 + 60 ) - 25 . 100`
`= 325 . 100 - 25 . 100`
`= 100 . ( 325 - 25 )`
`= 100 . 300`
`= 30000`
`c, 80 + [ 37 - ( 32 + 23 ) ]`
`= 80 + [ 37 - 55 ]`
`= 80 + ( - 18 )`
`= 62`
`d, 22 . 85 + 15 . 22 - 20200`
`= 22 . ( 85 + 15 ) - 202 . 100`
`= 22 . 100 - 202 . 100`
`= ( 22 - 202 ) . 100`
`= ( - 180 ) . 100`
`= - 18000`