.post-content h4 {
    padding-bottom: 20px;
    margin-bottom: 20px;
    border-bottom: solid 1px #4ab3b6;
    font-weight: bold;
    font-size: 22px;
    color: #4ab3b6;
    background-image: url(https://kumon-yatsushirotakashima.com/wp-content/uploads/2019/12/質問.png);
    background-repeat: no-repeat;
    line-height: 40px;
    padding-left: 65px!important;
}

@media only screen and (max-width: 767px){
.post-content h4 {
    padding-bottom: 15px;
    margin-bottom: 20px;
    background-size: 40px;
    font-size: 20px;
    line-height: 30px;
    padding-left: 55px!important;
}
}