`a ) {399 × 45 + 55 × 399}/{1995 × 1996 - 1991 × 1995}`
`= {399 × ( 45 + 55 )}/{1995 × ( 1996 - 1991 )}`
`= {399 × 100}/{1995 × 5}`
`= {399 × 100}/{399 × 5 × 5}`
`= 100/{5 × 5}`
`= 100/25 = 4`
`b ) {1996 × 1995 - 996}/{1000 + 1996 × 1994}`
`= {1996 × ( 1994 + 1 ) - 996}/{1000 + 1996 × 1994}`
`= {1996 × 1994 + ( 1996 - 996 )}/{1000 + 1996 × 1994}`
`= {1996 × 1994 + 1000}/{1000 + 1996 × 1994}`
`= 1`
`c ) {637 × 527 - 189}/{526 × 637 + 448}`
`= {637 × ( 526 + 1 ) - 189}/{526 × 637 + 448}`
`= {637 × 526 + ( 637 - 189 )}/{526 × 637 + 448}`
`= {637 × 526 + 448}/{526 × 637 + 448}`
`= 1`
`d ) {677 × 874 + 251}/{678 × 874 - 623}`
`= {677 × 874 + 251}/{( 677 + 1 ) × 874 - 623}`
`= {677 × 874 + 251}/{677 × 874 + ( 874 - 623 )}`
`= {677 × 874 + 251}/{677 × 874 + 251}`
`= 1`
`#dtkc`
