Aftrekken geeft \(4 p = 6 \text{,}\) dus \(p = 1\frac{1}{2} \text{.}\)

\(\begin{rcases}6 p - q = 2 \\ p = 1\frac{1}{2}\end{rcases} \begin{matrix}6 ⋅ 1\frac{1}{2} - q = 2 \\ -q = -7 \\ q = 7\end{matrix}\)

De oplossing is \((p , q) = (1\frac{1}{2} , 7) \text{.}\)

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

Aftrekken geeft \(-y = 4 \text{,}\) dus \(y = -4 \text{.}\)

\(\begin{rcases}4 x - 5 y = 2 \\ y = -4\end{rcases} \begin{matrix}4 x - 5 ⋅ -4 = 2 \\ 4 x = -18 \\ x = -4\frac{1}{2}\end{matrix}\)

De oplossing is \((x , y) = (-4\frac{1}{2} , -4) \text{.}\)

\(\begin{cases}5 a - 3 b = 6 \\ 2 a + 4 b = 5\end{cases}\) \(\begin{vmatrix}4 \\ 3\end{vmatrix}\) geeft \(\begin{cases}20 a - 12 b = 24 \\ 6 a + 12 b = 15\end{cases}\)

Optellen geeft \(26 a = 39 \text{,}\) dus \(a = 1\frac{1}{2} \text{.}\)

\(\begin{rcases}5 a - 3 b = 6 \\ a = 1\frac{1}{2}\end{rcases} \begin{matrix}5 ⋅ 1\frac{1}{2} - 3 b = 6 \\ -3 b = -1\frac{1}{2} \\ b = \frac{1}{2}\end{matrix}\)

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