Question RAM Speed decreased on Dell Laptop

[tian.ab]

I have a Dell Inspiron 3180 laptop with 4GB RAM running at 2400mhz. Then I decided to upgrade it to 8GB by switching the stick. My new RAM is supposed to run at 2666mhz but instead, it only shows 1200mhz. Is there any way to increase the RAM speed ?

 

[tian.ab]

Sorry the ram speed is covered in the original image, here's the task manager view

 

[Bob.B]

Sorry the ram speed is covered in the original image, here's the task manager view

It seems that 2400 is the max supported speed.
I doubt the dell bios allows overclocking.