中一數學

1.(+15)除(-3)=
2.(+28)除(+7)=
3.+2分之-14=
4.(-2)x(-5)x(-3)=
5.(-2)x(+5)分之(-6)x(+15)x(+4)=
最好有步驟啦,,
我唔識得乘的有向數...
唔該哂各位啦＾＾