Let's go through the questions in the image and solve them step by step.

Question 15:

The problem asks to write expressions for $x$ liters in different units, knowing that $x$ liters equals 1000 $x$ milliliters because there are 1000 mL in 1 L.

1. 15 a (i): cm³
   To convert liters to cubic centimeters (cm³):
   1 liter $= 1000 \, \text{cm}^3$
   Therefore, $x$ liters $= 1000x \, \text{cm}^3$.

2. 15 b (ii): m³
   To convert liters to cubic meters (m³):
   1 liter $= 0.001 \, \text{m}^3$
   Therefore, $x$ liters $= 0.001x \, \text{m}^3$.

3. 15 c (iii): kL
   To convert liters to kiloliters (kL):
   1 kiloliter $= 1000 \, \text{L}$,
   So $x$ liters $= \frac{x}{1000} \, \text{kL}$.

4. 15 d (iv): mL
   To convert liters to milliliters (mL):
   1 liter $= 1000 \, \text{mL}$,
   So $x$ liters $= 1000x \, \text{mL}$.

Question 16:

This question asks for the volume of a rectangular prism with length $l$, width $w$, and height $h$, expressed in different units.

1. 16 a (i): cm³
   The volume of a rectangular prism is given by $V = l \times w \times h$ in cubic centimeters.
   The expression for the volume in $\text{cm}^3$ is $V = l \times w \times h$.

2. 16 b (ii): m³
   To express the volume in cubic meters, convert the dimensions from centimeters to meters:
   1 cm = 0.01 m,
   So the volume $V = (l \times 0.01)(w \times 0.01)(h \times 0.01) \, \text{m}^3$,
   Simplifying, $V = l \times w \times h \times 10^{-6} \, \text{m}^3$.

3. 16 c (iii): L
   Since 1 liter $= 1000 \, \text{cm}^3$,
   Volume in liters is $V = \frac{l \times w \times h}{1000} \, \text{L}$.

4. 16 d (iv): kL
   To convert to kiloliters, knowing 1 kL = 1000 L:
   $V = \frac{l \times w \times h}{1000 \times 1000} = \frac{l \times w \times h}{1,000,000} \, \text{kL}$.

5. 16 e (v): mL
   Since 1 mL = 1 cm³,
   The volume in milliliters is $V = l \times w \times h \, \text{mL}$.

Would you like any further details on the calculations? Here are 5 related questions to think about:

1. How do you convert cubic meters to liters?
2. If you know the volume in kL, how would you convert that to cm³?
3. What is the difference between kiloliters and milliliters in terms of conversion?
4. How would you calculate the volume of a cylinder instead of a rectangular prism?
5. How does the conversion between units change if you're dealing with mass instead of volume?

Tip: Always remember to check unit consistency when performing volume calculations, especially when dimensions are provided in different units.