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:
calc() Otherwise calc() function will be invalid and the entire rule using it will be ignored.
.btn {
border: solid black 1px;
width: calc(100% 80px); /* Noncompliant */
}
.btn {
border: solid black 1px;
width: calc(100% - 80px);
}