Unit Conversions and Measurements

$20 \text{ km} = 3$ (Incomplete conversion, requires correct conversion factor or result)
$g = 88.66 \text{ kg}$ (This seems to assign a value to 'g', but 'g' is typically used for acceleration due to gravity. If it is mass, the correct notation is $m = 88.66 \text{ kg}$ .)
$mm = 40.436 \text{ cm}$ (This seems to equate millimeters to centimeters, which is incorrect. 1 mm = 0.1 cm, so this statement is false without additional context. Perhaps the intent was to convert a certain number of millimeters to centimeters.)
$_ 9 = 46.921 \text{ kg}$ (Typo or incomplete equation. Missing an operand on the left-hand side. The 9 is unclear. Requires context for understanding and completion.)
$48,500 \text{ m} = \text{ km}$ (Incomplete conversion. To convert meters to kilometers, divide by 1000. Therefore, $48,500 \text{ m} = 48.5 \text{ km}$ . The original notation lacks the result, which would properly complete the conversion.)

Unit Conversion: Converting values from one unit to another (e.g., meters to kilometers, millimeters to centimeters).
Mass Measurement: Measuring the quantity of matter in an object, typically in kilograms.
Mathematical Equations and Expressions: Correctly stating and completing equations to represent relationships between quantities.

Always specify units clearly when presenting measurements.
Ensure equations are complete and mathematically sound.
Double-check conversions for accuracy to avoid errors.
Pay attention to context when interpreting equations or measurements to understand the meaning.