Cant take screenshot on Acer A3-A20 tablet? help?

[JosephPlaysYT]

I've tried every combo (power and home, power and volume, power and volume down) and even tried installing some screenshot apps. There is no gesture screenshot so if anyone can help I'd love it! Thanks.

 

[annewoodhouse]

Yes by holding the power button and right hand corner of the sound button down together for apporox one second.