figure {
    text-align: center;
}
.projet_3_question_3 img {
    max-width: 8em;
    max-height: 8em;
}
.projet_4_question_1 {
    text-align: center;
}
.projet_4_question_1 figure {
    display: inline-block;
}
.projet_4_question_1 img {
    max-width: 8em;
    max-height: 8em;
}
.conteneurImage {
    text-align: center;
}
img.schema {
    max-width: 30em; 
    max-height: 30em;
}