`1)`
`a) A = -2; -1; 0; 1`
`b) x = 6`
`c) x = 13`
`2)`
`1)`
`a) -5 + -10 + 8 = ( -5 + -10 ) + 8`
`= -15 + 8 = -7`
`b) ( 189 - ( 34 + ( 20 - 5 ) ) ) : 20 = ( 189 - ( 34 + 15 ) ) : 20`
`= ( 189 - 49 ) : 20`
`= 140 : 20 = 7`
`c) 2^3 . 5^2 - 3^15 : 3^14 + 2019^0 . 1823`
`= 8 . 25 - 3 + 1823 = 200 - 3 + 1823`
`= 2020`
`2)`
`a) 2x + 15 = 27`
`2x = 27 - 15`
`2x = 12`
`x = 12 : 2`
`x = 6`
`b) 120 - ( x -15 ) = 170`
`( x - 15 ) = 120 - 170`
`x - 15 = - 50`
`x = -50 + 15`
`x = -35`
`c) |x - 7 | = 3`
`=> x - 7 = 3 ; x - 7 = -3`
`C1:x - 7 = 3`
`x = 7 + 3`
`x = 10`
`C2:x - 7 = -3`
`x = 7 + -3`
`x = 4`
Vậy `x = 10` hoặc `x= 4`
