Aftrekken geeft \(-4p=-8\text{,}\) dus \(p=2\text{.}\)

\(\begin{rcases}2p-q=-3 \\ p=2\end{rcases}\begin{matrix}2⋅2-q=-3 \\ -q=-7 \\ q=7\end{matrix}\)

De oplossing is \((p, q)=(2, 7)\text{.}\)

\(\begin{cases}5x+4y=5 \\ x+2y=-2\end{cases}\) \(\begin{vmatrix}1 \\ 2\end{vmatrix}\) geeft \(\begin{cases}5x+4y=5 \\ 2x+4y=-4\end{cases}\)

Aftrekken geeft \(3x=9\text{,}\) dus \(x=3\text{.}\)

\(\begin{rcases}5x+4y=5 \\ x=3\end{rcases}\begin{matrix}5⋅3+4y=5 \\ 4y=-10 \\ y=-2\frac{1}{2}\end{matrix}\)

De oplossing is \((x, y)=(3, -2\frac{1}{2})\text{.}\)

\(\begin{cases}5a+3b=5 \\ 2a-2b=-6\end{cases}\) \(\begin{vmatrix}2 \\ 3\end{vmatrix}\) geeft \(\begin{cases}10a+6b=10 \\ 6a-6b=-18\end{cases}\)

Optellen geeft \(16a=-8\text{,}\) dus \(a=-\frac{1}{2}\text{.}\)

\(\begin{rcases}5a+3b=5 \\ a=-\frac{1}{2}\end{rcases}\begin{matrix}5⋅-\frac{1}{2}+3b=5 \\ 3b=7\frac{1}{2} \\ b=2\frac{1}{2}\end{matrix}\)

De oplossing is \((a, b)=(-\frac{1}{2}, 2\frac{1}{2})\text{.}\)