Solution:

10 + 10 = 20
11 + 11 = 22 or we can say 20 too.

Solution:

1. The word "are" is repeated twice.
2. The word "to" is repeated twice.
3. The word mitstakes is misspelled. Its should be mistakes
4. The sentence is missing a punctuation mark and should end with a period/full stop not with semicolon.
5. Since there are only 4 mistakes, therefore, the statement of having five mistakes in the sentence is wrong which is the 5th mistake.

Solution:

123 - 45 - 67 + 89

Solution:

Turn it upside down as shown.

Solution:

Red or Tan

Explanation:
The numbers of letters in each color get reduced by one on every row.
Scarlet = 7
Orange and Yellow = 6
Green, Brown, and black = 5
Gray and Blue = 4
So the next color should be of three words like Red or Tan.

Solution:

82

Solution:

19

Solution:

He was a twin brother of one of Joseph's friends.

Solution:

Samuel should have come at 8 pm but he came home at 8:05 a.m i.e the next day.

Solution:

A Pizza.

Closed in a square box.
Mostly it's round.
Cut in a triangle shape.