How many lines are determined by three distinct points?

Find $d\left(A,B\right)$, if co-ordinates of $A$ and $B$ are $-2$ and $5$, respectively.

If $P-Q-R$ and $d(P,Q)=2, d(P,R)=10$, then find $d(Q,R)$.

On a number line, co-ordinates of $P, Q, R$ are $3$, $-5$ and $6$ respectively. State with reason whether the following statement is true or false.

$d\mathit{(}P\mathit{,}Q\mathit{)}\mathit{+}d\mathit{(}Q\mathit{,}R\mathit{)}\mathit{=}d\mathit{(}P\mathit{,}R\mathit{)}$.

On a number line, co-ordinates of $P, Q, R$ are $3$, $-5$ and $6$ respectively. Then $d\left(P,R\right)+d\left(R,Q\right)=d\left(P,Q\right)$.

On a number line, co-ordinates of $P, Q, R$ are $3$, $-5$ and $6$ respectively. State with reason whether the following statements are true or false.

$d\mathit{(}R\mathit{,}P\mathit{)}\mathit{+}d\mathit{(}P\mathit{,}Q\mathit{)}\mathit{=}d\mathit{(}R\mathit{,}Q\mathit{)}$

On a number line, co-ordinates of $P, Q, R$ are $3$, $-5$ and $6$ respectively. Then, $d\left(P,Q\right)=d\left(P,R\right)=d\left(Q,R\right)$.

If the distance between the pair of points whose coordinates are $3, 6$ is $k$ units, find the value of $k$

If the distance between the pair of points whose coordinates are $-9, -1$ is $k$ units, find the value of $k$