== Why is this an issue?

To perform calculations when specifying a CSS property ``++calc()++`` function can be used. This function takes single expression as parameter. When writing this expression some rules must be respected:

* no empty ``++calc()++``
* there should be an operator between the arguments
* there should not be any division by zero

Otherwise ``++calc()++`` function will be invalid and the entire rule using it will be ignored.


=== Noncompliant code example

[source,css]
----
.btn {
  border: solid black 1px;
  width: calc(100% 80px);  /* Noncompliant */
}
----


=== Compliant solution

[source,css]
----
.btn {
  border: solid black 1px;
  width: calc(100% - 80px);
}
----