`\text{a)}`
`2023 1/4 - 25% . (-1)^2020 -1,8 :3/5`
`= 2023 1/4 - 1/4 - 3`
`= 2023 -3`
`= 2020`
`\text{b)}`
Đặt `A =20/{1.6} + 20/{6.11 } + ...+ 20/{101.106}`
`-> 1/4A = 5/{1.6} + 5/{6.11} + .... + 5/{101.106}`
`-> 1/4A = 1 - 1/6 +1/6 -1/11 + ... + 1/101 - 1/106`
`-> 1/4A =1 -1/106`
`-> 1/4 A = 105/106`
`-> A = 105/106 . 4`
`-> A = 210/53`
