I have two questions: first, why my paragraph and my paragraph2 are display, second, my two p is not concat. Thanks you.

Question

Display p and concat two p.
https://code.sololearn.com/W1BXITcMXE30/?ref=app

Answer 1

Do you know what is an undefined variable?

in add method you uses all params but only two arguments are passed.

the you get this error on line 8.