How does real numbers in/become useful in real world situations?

I don’t understand, like just numbers? In building they use numbers to find how much they need for the building. Employees find the total cost they need to charge you. Please give me a bit more of info if this doesn’t help

Numbers are every where. If you want to find out which type of orange juice is a better deal in a supermarket, you will use numbers. Everywhere you go there will be numbers. Just think about it. There in schools, there in restaurants, there everywhere! I hope this helps your question!  :)

Yes, two vertical lines can be complementary