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<div class="block">
  <div class="inner">

  <span>строка</span>
<span>строка строка строка строка</span>
<span>строка строка строка</span>
</div>
</div>
* {
  box-sizing: inherit;
}

html {
  box-sizing: border-box;
}
body {
  margin: 0;
}

.block {
  background: blue;
  padding: 40px;
}
.inner {
  display: inline-block;
  background: linear-gradient(to bottom, #FC4E3C, yellow);
  font-size: 20px;
  text-transform: uppercase;
}
.inner span {
  display: flex;
  line-height: 1.5;
}
.inner span::after {
  content: "";
  flex: 1;
  background: blue;
}