1) ` ( 15 + 37 ) + ( 52 - 37 - 17 ) `
` = 15 + 37 + 52 - 37 = 17`
`= 15 + 37 + 52 - 37 - 17`
`= 37 - 37 + 52 + 15 - 17`
`= 0 + 52 + 15 - 17`
`= 67 - 17 = 50 `
2) `( 38 - 42 + 14 ) - ( 25 - 27 - 15 ) `
`= 38 - 42 + 14 - 25 + 27 + 15 `
`= 38 + 42 + 14 - 25 + 27 + 15`
`= -4 + 14 - 25 + 27 + 15 `
`= 10 - 25 + 27 + 15 `
`= [ (-15) + 15 )] + 27 `
`= 27 `
3 ) ` - ( 21 - 32 ) - ( - 12 + 32 ) `
`= - 21 + 32 + (-12 ) + 32 `
`= 11 - [(-12 ) + 32 ] `
`= 11 - 20 = - 9 `
4) ` -(12 + 21 - 23 ) - ( 23 - 21 + 10 ) `
`= - 12 - 21 + 23 - 23 + 21 - 10 `
`= ( 21 - 21 ) + ( 23 - 23 ) - ( 12 + 10) `
`= 0 + 0 - 22 = -22 `
5 ) ` (57 - 725) - (605 - 53 )`
`= 57 - 725 - 605 + 53 `
`= ( 57 + 53 ) - ( 725 + 605 ) `
`= 110 - 1330 = 1220`
6 ) ` ( 55 + 45 + 15 ) - ( 15 - 55 + 45 ) `
`= 55 + 45 + 15 - 15 + 55 - 45 `
`= 55 + 55 = 110 `
7) ` ( 35 + 75 ) + ( 345 - 35 - 75 ) `
`= 35 + 75 + 345 - 35 - 75 `
`= ( 35 + 75 )+ (345 - 35 ) - 75
`= 110 + (310 - 75 )
`= 110 + 235 = 345 `
8) ` ( 2002 - 79 + 15 ) - ( -79 + 15 ) `
`= 2002 - 79 + 15 - (-79 ) - 15 `
`= 2002 - [ 79 + ( -79 ) ] + ( 15 - 15 ) `
`= 2002 - 0 - 0 = 2002 `
9) ` -(515 - 80 + 91 ) - ( 2003 + 80 - 91 ) `
`=-515 + 80 - 91 - 2003 - 80 + 91 `
`=(-515 + 2003 ) + ( 80 - 80 ) + ( 91 - 91 )`
`= -2518 + 0 + 0 = -2518`
