<sup> with CSS

HTML

<span class="price">39
  <span class="cents">99</span>
  <span class="zl">zł/mies.</span>
</span>

CSS

.price {
    font-size:60px;
}
.cents {
    vertical-align: super;
    font-size:30px;
}
.zl {
  vertical-align: sub;
  font-size:12px;
}