#resImage_300 {
    display:block;
    overflow:hidden;
    background-image:url('https://perform.campden.school.firthdesign.co.uk/assets/images/9/support-us-cda4babf.jpg');
    background-repeat:no-repeat;
    background-position:center center;
        width:100%;
    background-size: cover;
        height:450px;
}
@media screen and (min-width:700px){
    #resImage_300 {
        background-image:url('https://perform.campden.school.firthdesign.co.uk/assets/images/3/support-us-b11071e8.jpg');
                height:400px;
    }
}
@media screen and (min-width:980px){
    #resImage_300 {
        background-image:url('https://perform.campden.school.firthdesign.co.uk/assets/images/3/support-us-257f8f64.jpg');
                height:400px;
    }
}
@media screen and (min-width:1400px){
    #resImage_300 {
        background-image:url('https://perform.campden.school.firthdesign.co.uk/assets/images/2/support-us-b7a048d1.jpg');
                height:450px;
    }
}