```x``` Specify the start of the range in which to interpolate.
```y``` Specify the end of the range in which to interpolate.
```a``` Specify the value to use to interpolate between x and y.
### Description
```mix()``` performs a linear interpolation between ```x``` and ```y``` using ```a``` to weight between them. The return value is computed as ```x×(1−a)+y×a```.