1. mit 30y multiplizieren
\(6\cdot 10+10y\cdot 7 =15y\cdot 3-10(2y-3)-15\cdot 5\)
\(60+70y =45y-20y+30-75\)
\(60+70y = 25y -45\)
\(45y = -105\)
\(y=-\dfrac{105}{45}=-\dfrac{7}{3}\)
2. \(x=1\)
3.
\( \begin{aligned} \frac{3c}{d-cx}+\frac{cd}{dx-cx^2} & =\frac{2c}{x} \\ \frac{3c}{d-cx}+\frac{cd}{x(d-cx)} & =\frac{2c}{x}~~~~~~~~&|\cdot x(d-cx) \\ 3c\cdot x+ cd & =2c\cdot(d-cx) \\ 3c\cdot x+ cd & =2cd-2c^2x &|-cd+2c^2x \\ 3c\cdot x+2c^2x & =cd &|~~cx \text{ ausklammern} \\ x\cdot c\cdot(3+2c) & =cd &|\cdot\frac{1}{c(3+2c)} \\ x & =\frac{d}{3+2c} \end{aligned} \)