<div class="row">
  <div class="card">
    <div class="card-content"></div>
  </div>
  <div class="card">
    <div class="card-content"></div>
  </div>
  <div class="card">
    <div class="card-content"></div>
  </div>
  <div class="card">
    <div class="card-content"></div>
  </div>
  <div class="card">
    <div class="card-content"></div>
  </div>
</div>

<div class="row">
  <div class="card">
    <div class="card-content"></div>
  </div>
  <div class="card">
    <div class="card-content"></div>
  </div>
  <div class="card">
    <div class="card-content"></div>
  </div>
  <div class="card">
    <div class="card-content"></div>
  </div>
</div>

* {
  box-sizing: border-box;
}

.row {
  display: flex;
  flex-wrap: wrap;
  margin: 0 -15px 30px;
}

.card {
  flex: 1 0 33%;
  padding: 0 15px;
  margin-bottom: 15px;
}

.card-content {
  height: 100px;
  border-radius: 10px;
  background-color: #888;
}