Aşağıdaki kodlarla 4 tane yan yana div yapmak istiyorum. olmuyor hata nerde bu kodlarda?

.grid-three-layout .post {
    width: calc( 20% - 14px );
    float: left;
}

.grid-three-layout .post:nth-of-type(4n-1), .grid-three-layout .post:nth-of-type(4n-2) { margin-right: 21px }
.grid-three-layout .post:nth-of-type(4n-2), .grid-three-layout .post:nth-of-type(4n-3) { margin-right: 21px }
.grid-three-layout .post:nth-of-type(4n-3), .grid-three-layout .post:nth-of-type(4n-4) { margin-right: 21px }
.grid-three-layout .clearfix:nth-of-type(4n-3), .grid-three-layout .clearfix:nth-of-type(4n-4) { display: none }