justify-content: space-around

a1 a2 a3
a1; height: 30px a2; height: 30px a3; height: 30px
a1; flex-basis: 30px a2; flex-basis: 30px a3; flex-basis: 30px

flex-grow: 1

a1 a2; flex-grow: 1
a1; flex-grow: 1 a2; flex-grow: 1
a1; flex-grow: 1 a2; flex-grow: 3 a3; flex-grow: 1

margin: auto

a1; margin: 0 auto a2; margin: 0 auto
a1; margin: 0 auto a2; margin: 0
a1; margin: 0 a2; margin: 0 auto
a1; margin: 0 auto a2; margin: 0 auto a3; margin: 0 auto

align-items: flex-end; justify-content: flex-end

a1 a2

order: 1

a1; order: 1 a2; order: 0