219.00 + 159.00 = 378.00, the lowest cost of DJ & lights
369.00 + 309.00 = 678.00, the highest cost of DJ & lights
This means the lowest cost would be $434.00, and the highest cost would be $678.00, which written as our compound inequality:
$378.00 ≤ x ≤ $678.00
If we wanted to write it as an interval format, it would look like:
[$378.00, $678.00] (We use brackets because it's less/greater than or equal to those amounts.)