A landscaper planted 5 rows of 4 trees each for a family. He was asked later that day how many trees he planted. He responded "5 rows of 4 trees each". The person said, "You planted 20 trees then?" The landscaper said, "No, i did not, but I did plant 5 rows of 4 trees each". How did this happen?

I am hired to do something and do it, it becomes crucial and I fail, not one but twice. People count on me and I don't come through at huge moments. I obviously have no feeling in my knee. Who am I?

10 x 2, and 11 x 2 get the same answer. How?

I am the first thing you need when camping,
I am always with people named Carl and Marco,
Peter thinks I'm useless and doesn't need me.
I am the second to last thing to add when making a taco.
What am I?

I can be scary or terrifying, I can be the sweetest thing you've ever seen, I can be anything you want me to be, what am I?