.videoBlock{width:calc(25% - 12px);}

@media only screen and (min-width:1024px) {
    .threeBlocks .videoBlock {
        width: calc(33.3% - 12px);
    }
}

@media only screen and (max-width:1023px) {
    .videoBlock{
        width: calc(50% - 14px);
    }
}

@media only screen and (min-width:480px) and (max-width: 1023px) {
    .threeBlocks .videoBlock {
        width: calc(50% - 12px);
    }
}

@media only screen and (max-width:479px) {
    .videoBlock {
        width: calc(100% - 12px);
    }
}