如何设置元素的百分比宽度

.content_sort_average_select{
                display: flex;
                justify-content: space-around;
                flex-wrap: wrap;
                .content_sort_average_select_li{
                    display: flex;
                    align-items: center;
                    justify-content: center;
                    margin: 10rpx 0;
                    height: 60rpx;
                    background-color: #FAFAFA;
                    font-size: 30rpx;
                    width: calc((100% / 3) - 30rpx);
                }
            }

Snipaste_2020-09-01_13-31-57.png

和
flex-wrap: wrap;
搭配使用