.section-formula{
  position: relative;
  background: #0b1220; /* o tu gradiente */
}

.section-formula::before{
  content:"";
  position:absolute;
  inset:0;
  background: rgba(0,0,0,.35); /* ajusta 0.25–0.45 */
  z-index:0;
  pointer-events:none;
}

.section-formula .content,
.section-formula .container,
.section-formula .wrap{
  position: relative;
  z-index:1;
}