Solve for x in the following equations: 9(ii) 5x = 3, and 9(iii) 50/(1+e^-x) = 4.

Step 1: Complete the solution for 9(ii).
From the previous step, we had:

$$5x = 3$$

Divide by 5:

$$x = \frac{3}{5}$$

The solution is $\boxed{x = \frac{3}{5}}$.

Step 2: Solve 9(iii) $\frac{50}{1+e^{-x}} = 4$.
Multiply both sides by $(1+e^{-x})$:

$$50 = 4(1+e^{-x})$$

Divide by 4:

$$\frac{50}{4} = 1+e^{-x}$$ $$$$