`a ) 80 - [ 130 - ( 12 - 4 )^2]`
`= 80 - [ 130 - 8^2 ]`
`= 80 - [ 130 - 64 ]`
`= 80 - 66`
`= 14`
`b ) 23 × 75 + 25 × 23 - 130`
`= 23 × ( 75 + 25 ) - 130`
`= 23 × 100 - 130`
`= 2300 - 130`
`= 2170`
`c ) 15 × 37 × 4 + 42 × 60 + 21 × 5 × 12`
`= ( 15 × 4 ) × 37 + 42 × 60 + ( 12 × 5 ) × 21`
`= 60 × 37 + 42 × 60 + 60 × 21`
`= 60 × ( 37 + 42 + 21 )`
`= 60 × 100`
`= 6000`
`d ) 5 × 25 × 2 × 16 × 4`
`= ( 5 × 2 ) × ( 4 × 25 ) × 16`
`= 10 × 100 × 16`
`= 1000 × 16`
`= 16000`
`e ) 4 × 24 × 5^2 - ( 3^3 × 18 + 3^3 × 12 )`
`= 4 × 24 × 25 - ( 27 × 18 + 27 × 12 )`
`= ( 4 × 25 ) × 24 - 27 × ( 18 + 12 )`
`= 100 × 24 - 27 × 30`
`= 2400 - 810`
`= 1590`
`#dtkc`