lesson 13

question 1

question 1.1

question 2

question 3

question 3.4

question 3.5

question 3.6

question 3.6.1

question 3.6.2

question 3.6.3

question 3.6.4

question 5

question 7

question 8

question 9

question 10

question 11

question 12