Here, we will use the below rules,
`(+)xx(-) = (-)`
`(-)xx(+) = (-)`
`(-)xx(-) = (+)`
`(+)xx(+) = (+)`
(a)`3xx(-1) = -3`
(b)`(-1)xx225 = -225`
(c)`(-21)xx(-30) = 630`
(d)`(-316)xx(-1) = 316`
(e)`(-15)xx0xx(-18) = 0`
(f)`(-12)xx(-11)xx(10) = 1320`
(g)`9xx(-3)xx(-6) = 162`
(h)`(-18)xx(-5)xx(-4) = -360`
(i)`(-1)xx(-2)xx(-3)xx4 = -24`
(j)`(-3)xx(-6)xx(-2)xx(-1) = 36`