Unexpected situations

What do you do when a friends ask you to do something but you have not asked your parents for permission to go there?

I tell him that I can not go and I get out of the situation and then I ask my parents for permission and if they tell me that if I tell my friend that I cancel the commitment and that if I can go.

Did you have an unexpected situation in the school?

If normally when I have to deliver a job or expose on computers and something happens that I did not expect as they did not do their part or I forgot my part