It is not imperative to always start with the largest network but it is easier if you're not accustomed with sub-netting.
You can take it this way:
Divide your 10.97.21.0/24
network into 2 /25 networks:
10.97.21.0/25
10.97.21.128/25
Since you need a /25, keep one and further subnet the other one, once again in two networks:
10.97.21.0/25
10.97.21.128/26
10.97.21.192/26
You need a /26, so you keep the first one and divide the other one in two:
10.97.21.0/25
10.97.21.128/26
10.97.21.192/27
10.87.21.224/27
as you can see we get the solution given by @Datagram.Network, but if choose instead to divide the first subnet and keep the second we can also have
10.97.21.0/27
10.97.21.32/27
10.97.21.64/26
10.87.21.128/25
For more information you may find this answer to How do you calculate the prefix, network, subnet, and host numbers? interesting