help meeeeeeeeeeeeeeeee

`a.`

`A = 4a - 3b`

`text{Thay a = -7 , b = -5}`

`A = 4 . ( -7 ) - 3 . (-5)`

`A = ( -28 ) -  ( -15 )`

`A = -13`

`b. `

`B = a(b + 9 ) + 5a `

`text{Thay a = -7 , b = -5}` 

`B = ( -7 ) . ( -5 + 9 ) + 5 . ( -7 )`

`B = ( -7 ) . 4 + 5 . ( -7 )`

`B = (-28 ) + (-35)`

`B = -63 `

`c. `

`C = ( -15 )a + ( -7 ) . b`

`text{Thay a = -7 , b = -5 }`

`C = ( -15 ) . ( -7 ) + ( -7 ) . ( -5 )`

`C = 105 + 35`

`C = 140 `

`d.`

`D = ( 315 - 427 )a + (46 - 89 ).b`

`text{Thay a = -7 , b = -5}`

`D = ( 315 - 427 ) . (-7) + (46 - 89 ). ( -5 )`

`D = ( -112 ) . ( -7 ) + ( -43 ) . ( -5 )`

`D = 784 + 215`

`D = 999`