a) Thay x=6-y
ta có: \(\frac{6-y+3}{y+5}=\frac{3-y}{y+5}=\frac{3}{5}\)
\(\Rightarrow\left(3-y\right).5=\left(y+5\right).3\)
15 - 5y= 3y + 15
-5y-3y=15-15
-8y=0
y=0
Vậy x=6
b) Thay x= y-4
ta có: \(\frac{y-4-7}{y-6}=\frac{y-11}{y-6}=\frac{7}{6}\)
\(\Rightarrow\left(y-11\right).6=\left(y-6\right).7\)
6y-66 = 7y -42
-y=24
y=-24
Vậy x=-4+-24=-28
\(\frac{x+3}{y+5}=\frac{3}{5}\\ \Leftrightarrow5\left(x+3\right)=3\left(y+5\right)\\ \Leftrightarrow5x+15=3y+15\\ \Leftrightarrow5x=3y\\ M\text{à};x+y=6\Rightarrow x=6-y\\ \Rightarrow5\left(6-y\right)=3y\\ \Leftrightarrow30-5y=3y\\ \Rightarrow30=8y\\ \Rightarrow y=\frac{30}{8}\\ \)
\(\frac{x-7}{y-6}=\frac{7}{6}\\ \Leftrightarrow6\left(x-7\right)=7\left(y-6\right)\\ \Leftrightarrow6x-42=7y-42\\ \Leftrightarrow6x=7y\\ M\text{à}x-y=-4;\Rightarrow x=-4+y\\ \Rightarrow6\left(-4+y\right)=7y\\ \Rightarrow-24+6y=7y\\ \Rightarrow y=-24\\ \)
Từ y bạn từ tìm x nhé!!!