$\text{Câu 1:}$
`a, 1/4 + 3/4 . ((-1)/2 + 2/3)`
`= 1/4 + 3/4 . ((-3)/6 + 4/6)`
`= 1/4 + 3/4 . 1/6`
`= 1/4 + 1/8`
`= 2/8 + 1/8 = 3/8`
`b, 0,5 . 1 1/3 . 75% : (-2)/5 + 3/5`
`= 1/2 . 4/3 . 3/4 . (-5)/2 + 3/5`
`= (-5)/4 + 3/5`
`= (-25)/20 + 12/20 = (-13)/20`
`c, (-3)/7 . 5/9 + 4/9 . (-3)/7 + 2 3/7`
`= (-3)/7 . (5/9 + 4/9) + 17/7`
`= (-3)/7 . 1+ 17/7 = 2`
$\text{Bài 2:}$
`a, 1 3/8 x - 1/4 = 1/2`
`⇒ 11/8 x = 1/2 + 1/4`
`⇒ 11/8 x = 2/4 + 1/4`
`⇒ 11/8 x = 3/4`
`⇒ x = 3/4 : 11/8`
`⇒ x = 3/4 . 8/11`
`⇒ x = 6/11`
`b, (50% x + 2 1/4) . (-2)/3 = 17/6`
`⇒ 1/2 x + 9/4 = 17/6 : (-2)/3`
`⇒ 1/2 x + 9/4 = 17/6 . (-3)/2`
`⇒ 1/2 x + 9/4 = (-17)/4`
`⇒ 1/2 x = (-17)/4 - 9/4`
`⇒ 1/2 x = (-13)/2`
`⇒ x = (-13)/2 : 1/2`
`⇒ x = (-13)/2 . 2`
`⇒ x = -13`
`c, 11 - |2x + 8| = 20`
`⇒ |2x + 8| = 11 - 20`
`⇒ |2x + 8| = -9`
$\text{⇒ x không có giá trị thỏa mãn}$
