`a, ( - 7 )/25 . 39/-14 . 50/78`
`= ( ( - 7 ) . 39 . 50 )/( 25 . ( - 14 ) . 78 )`
`= ( ( - 7 ) . 39 . 2 . 5 . 5 )/( 5 . 5 . 2 . ( - 7 ) . 39 . 2 )`
`= 1/2`
`b, 6/7 . 8/13 + 6/13 . 9/7 - 3/13 . 6/7`
`= 6/7 . ( 8/13 - 3/13 ) + ( 6 . 9 )/( 7 . 13 )`
`= 6/7 . 5/13 + 6/7 . 9/13`
`= 6/7 . ( 5/13 + 9/13 )`
`= 6/7 . 14/13`
`= 12/13`
`c, ( ( - 9 )/25 . 5^3 )/( 3 - ( ( - 3 )/5 )^2 . 22/3 )`
`= ( ( - 9 )/25 . 125 )/( 3 - 9/25 . 22/3 )`
`= ( - 45 )/( 3 - 66/25 )`
`= ( - 45 )/( 9 /25 )`
`= ( - 45 ) : 9/25 = - 125`
