How many dashes are there?

$\begin{aligned} & \underbrace{ 6-6-6-\cdots - 6}_{\text{number of 6's }=\, 50} = \underbrace{9-9-9-\cdots - 9}_{\text{ number of 9's }=\, N} \\& 6 - 6(\underbrace{1+1+1\cdots + 1}_{\text{number of 1's } =\, 49}) = 9 - 9(\underbrace{1+1+1+\cdots+1}_{\text{number of 1's }=\, x (say)})\end{aligned}$ From above we get . $\begin{aligned} & 6- 6.49 = 9-9x \\ & -6.48 = 9(1-x)\\& \Rightarrow x = 33 \end{aligned}$ So required numbers of $N = 34$ since $N=x+1$ .

We can evaluate the first 2 terms on either side to equal 0. This means that we are left with $48 \times -6$ on the left hand side and $(N-2) \times -9$ on the right. Therefore, $48 \times -6 = -9(N-2)$ $-288 = -9(N-2)$ $32 = N-2$ $N=\boxed{34}$