`60 : [ 7 - ( 11^2 - 20 . 6 ) + 5 ]`
`= 60 : [ 7 - ( 121 - 120 ) + 5 ]`
`= 60 : [ 7 - 1 + 5 ]`
`= 60 : [ 6 + 5 ]`
`= 60 : 11`
`= 60/11`
`---`
`135 + 3 . 5^{2x - 1} = 510`
`3 . 5^{2x -1} = 510 - 135`
`3 . 5^{2x -1} = 375`
`5^{2x -1} = 375 : 3`
`5^{2x -1} = 125`
`5^{2x -1} = 5^3`
`=> 2x - 1 = 3`
`2x = 3 + 1`
`2x = 4`
`x = 4 : 2`
`x = 2`
Vậy `x= 2`
`---`
`[( 102 - x ) × 3 - 51] : 3 - 2 = 3`
`[( 102 - x ) × 3 - 51] : 3 = 3 + 2`
`[( 102 - x ) × 3 - 51] : 3 = 5`
`( 102 - x ) × 3 - 51 = 5 × 3`
`( 102 - x ) × 3 - 51 = 15`
`( 102 - x ) × 3 = 15 + 51`
`( 102 - x ) × 3 = 66`
`102 - x = 66 : 3`
`102 - x = 22`
`x = 102 - 22`
`x = 80`
Vậy `x = 80`
`#dtkc`
