The way you combine the /24 subnets is to change the subnet mask to a /22. (ie. 255.255.252.0) This makes it all one contiguous address space. Just change the subnet mask to 255.255.252.0 and ...

I came across this very odd note about subnetting in my CCNA study guide. For those who have it, the book is Sybex's CCNA Study Guide, 4th Edition. Page 109: We're going to subnet the network address ...