Answers for "3 col bootstrap"

columns center bootstrap 3

<div class="row">
    <div class="col-md-2 col-md-offset-5"></div>
</div>

bootstrap breakpoints

// Extra small devices (portrait phones, less than 576px)
// No media query since this is the default in Bootstrap

// Small devices (landscape phones, 576px and up)
@media (min-width: 576px) { ... }

// Medium devices (tablets, 768px and up)
@media (min-width: 768px) { ... }

// Large devices (desktops, 992px and up)
@media (min-width: 992px) { ... }

// Extra large devices (large desktops, 1200px and up)
@media (min-width: 1200px) { ... }

.row bootstrap

.row{
    display: flex;
    flex-wrap: wrap;
	margin-right: -15px;
    margin-left: -15px;
}

.col-12 bootstrap

.col-12{
	flex: 0 0 100%;
	max-width: 100%;
}