An equation:
It is used to express exact values.
Therefore, we will use an equation when when know that the quantity given is strictly equal to a given value.
Examples:
1- Price of a kilo of apples is $2
This is translated as ........> cost of 1 kilo = $2
2- The length of a ruler is 30 cm
This is translated as ......> length = 30 cm
An inequality:
It is used to show relation or compare between a quantity and a value. Therefore, we use it when we find keywords as "at least, at most, greater than, less than, ..... etc"
Example:
1- The distance between two cities is at least 20 miles.
This means that the distance can be 20 miles or more
This is translated as:
distance ≥ 20 miles