\(\dfrac{-3}{x+1}=\dfrac{4}{2-2x}\)

\(\Rightarrow\left(-3\right).\left(2-2x\right)=4.\left(x+1\right)\)

\(\Rightarrow-6+6x=4x+4\)

\(\Rightarrow6x-4x=4+6\)

\(\Rightarrow2x=10\)

\(\Rightarrow x=10:2\)

\(\Rightarrow x=5\)

nhiều quà xịn mà ngu sinh:(

Các bạn thi tốt nhé mìn ko giỏi sinh nên thoi:)

Số đó là : 

\(12,5\times100:25=50\)

hi

\(2057,75-\left(36+12,6\right):0,9\times0,5\)

\(=2057,75-48,6:0,9\times0,5\)

\(=2057,75-54\times0,5\)

\(=2057,75-27\)

\(=2030,75\)

\(\left(3+5+7+...+2021\right)\times\left(6,2:0,25-2,48\times10\right)\)

\(=\left(3+5+7+...+2021\right)\times\left(24,8-2,48\times10\right)\)

\(=\left(3+5+7+...+2021\right)\times\left(24,8-24,8\right)\)

\(=\left(3+5+7+...+2021\right)\times0\)

\(=0\)