Toán Lớp 6: Câu 2: Tìm x biết: a) 12 + (5 + x) = 20 b) 175 + (30 – x) = 200 c) 10 + 2x = 45 : 43 d) 10x + 22.5 = 102

Question

Toán Lớp 6:  Câu 2: Tìm x biết: a) 12 + (5 + x) = 20 b) 175 + (30 – x) = 200 c) 10 + 2x = 45 : 43 d) 10x + 22.5 = 102

ngoclanhoa · Answer

a. 12+ (5+x) = 20   5+x = 20 -12   5+ x = 8   x= 8-5   x=3   B. 175 + (30-x) =200   30+x = 200-125   30+x =25   x=25-30   x= -5   c. 10 +2x =45:43   10x +2x = 45/43   2x = -385/43   x= -386/56   d. 10x + 22.5 =102   10????+110 = 102   10x= -8   c= -8/10

ngoclankhue · Answer

a, 12 + (5 + x) = 20   $ Rightarrow$ (5 + x) = 20 - 12   $ Rightarrow$ 5 + x = 8   $ Rightarrow$ x = 8 - 5   $ Rightarrow$ x = 3   $ text{Vậy}$ x = 3   ______________________   b, 175 + (30 - x) = 200   $ Rightarrow$ (30 - x) = 200 - 175   $ Rightarrow$ 30 - x = 25   $ Rightarrow$ x = 30 - 25   $ Rightarrow$ x = 5   $ text{Vậy}$ x = 5   _____________________   c, 10 + 2x = 45 : 43   $ Rightarrow$ 10 + 2x = 45/43   $ Rightarrow$ 2x = 45/43 - 10   $ Rightarrow$ 2x = -385/43   $ Rightarrow$ x = -385/43 : 2   $ Rightarrow$ x = -385/86   $ text{Vậy}$ x = -385/86   _______________________   d, 10x + 22 . 5 = 102   $ Rightarrow$ 10 x + 110 = 102   $ Rightarrow$ 10x = 102 - 110   $ Rightarrow$ 10x = -8   $ Rightarrow$ x = -8 : 10   $ Rightarrow$ x = -4/5   $ text{Vậy}$ x = -4/5