.formula,
.letters {
    margin-top: 2px;
    margin-bottom: 2px;
    color: black;
    padding: 0.5rem;
    padding-bottom: 1px;
    margin-bottom: 0.5rem;
}

.formula p:last-child,
.letters p:last-child {
    padding-bottom: 0;
}

.formula {
    background: lightblue;
}

.letters {
    background: lightyellow;
}