$\\$
Bài `1.`
`( (-1)/4 + 7/33 - 5/3) - ( (-15)/12 + 6/11 - 48/49)`
`= (-1)/4 + 7/33 - 5/3 + 15/12 - 6/11 + 48/49`
`= ( (-1)/4 - 5/3 + 15/12) + (7/33 - 6/11) + 48/49`
`= ( (-3)/12 - 20/12 + 15/12) + (7/33 - 18/33) + 48/49`
`=(-2)/3 + (-1)/3 + 48/49`
`= -1 + 48/49`
`= (-49)/49 + 48/49`
`= (-1)/49`
$\\$
Bài `2.`
`a,`
`1 4/5 = -0,15 -x`
`-> (-3)/20 - x = 9/5`
`-> x=(-3)/20 - 9/5`
`-> x=(-3)/20 - 36/20`
`-> x=(-39)/20`
Vậy `x=(-39)/20`
`b,`
`(3/8 - 1/5) + (5/8 - x) = 1/5`
`->3/8 - 1/5 + 5/8 - x - 1/5=0`
`-> (3/8 + 5/8) + ( (-1)/5 - 1/5)-x=0`
`-> 1 -2/5 - x=0`
`-> 5/5 - 2/5 -x=0`
`-> 3/5- x=0`
`->x=3/5-0`
`->x=3/5`
Vậy `x=3/5`
`c,`
`9/2 - [2/3 - (x+7/4)] = (-5)/4`
`-> 2/3 - (x+7/4) = 9/2 + 5/4`
`-> 2/3 - (x+7/4) = 18/4 + 5/4`
`-> 2/3 - (x+7/4)=23/4`
`-> x + 7/4 = 2/3 - 23/4`
`-> x + 7/4 = 8/12 - 69/12`
`-> x+7/4=(-61)/12`
`->x=(-61)/12 - 7/4`
`->x=(-61)/12 - 21/12`
`->x=(-41)/6`
Vậy `x=(-41)/6`
