A55M-DS2
Socket FM1
DDR3 1866/1600/1333/1066 MHz
1 slot PCI Express x 16 (x16)
A8-3870K
Socket FM1
This cpu is compatible with this motherboard. (http://www.cpu-upgrade.com/mb-Gigabyte/GA-A55M-DS2(rev._1.0).html)
GTX 750 Ti
PCI Express x16
Yes, those components should work together 😉