#ex15_case1,#ex15_case2,#ex15_case3,#ex15_case4{
width: 4em;
}

#cadre1{
float:left;
width:430px;
background-color: #eee;
}

#enonce_ex15{
position:relative;
left:0;
top:-40px;
 color:#000000;
 font-size:1.0em;
}