Yes, it will.
Ill say, no you cant. Own a Gigabyte 9800Gt Silent Cell. Have some problems with a stalling computer after a while playing games. I quess you can, but its not recommended.
Primary PCIe slot
The best performance: ASUS ROG ARES II Radeon HD 7990 The Best for Performance and price: GeForce GTX 680
No. You will need to replace your motherboard to get PCI-E.
computer full form
type of chipset
A gaming motherboard should have at least two PCIe slots for Crossfire or SLI video cards.
Most likely for dual graphics cards.
300 watts
The best PCIe video cards on the market today are the nVidia 285 and 295 series.
The ASUS M5A78L-M USB3 motherboard features a PCIe x16 slot, which allows for compatibility with a variety of graphics cards. Suitable options include AMD Radeon cards like the RX 500 series or NVIDIA GeForce GTX 1000 series. However, the choice of graphics card should also consider your power supply and case size. Always check for compatibility regarding power requirements and physical dimensions before purchasing.
I presume that you mean to ask whether a PCIe 3.0 card can be used in a PCIe 2.0 slot on your motherboard. The answer to that question is yes. PCIe standards are all backward-compatible, so do not sweat that. For best performance, however, you would prefer to put a PCIe 3.0 card in the same type of slot.