a) `(1/7)^2020 . 7^2020`
`= (1/7 . 7)^2020`
`= 1^2020`
`= 1`
b) `2010/2021 . 13/18 + 2020/2021 . 5/18`
`= 2010/2021 . 13/18 + (2010+10)/2021 . 5/18`
`=2010/2021 . 13/18 + (2010/2021 + 10/2021) . 5/18`
`= 2010/2021 . 13/18 + 2010/2021 . 5/18 + 10/2021 . 5/18`
`= 2010/2021 . (13/18 + 5/18) + 10/2021 . 5/18`
`= 2010/2021 . 1 + 10/2021 . 5/18`
`= 2010/2021 + 25/18189`
`= 18090/18189 + 25/18189`
`= 18115/18189`
a) `x - 1/3 = 1/2`
`⇒ x = 1/2 + 1/3`
`⇒ x = 5/6`
b) `|x + 1/2| = 5/4`
`TH1 : x + 1/2 = 5/4`
`⇒ x = 5/4 - 1/2`
`⇒ x = 3/4`
`TH2 : x + 1/2 = -5/4`
`⇒ x = -5/4 - 1/2`
`⇒ x = -7/4`
