Weknow.ac is unwanted search engine on Chrome

I have been having ongoing problems with my Mac for perhaps months. I've talked to Apple support at least 3 times. I've noticed that the "search engine" WeKnow.ac is installed in my Chrome browser as the preferred one but I never preferred it and don't want it. It may be causing a phony Google screen to appear when I try to use Google.

I've had problems using Safari too and think maybe Weknow.ac is infecting it as well. I've found directions for getting rid of Weknow by deleting lines in Terminal but I haven't tried it yet. It looks complicated. I'd like some advice. Thanks, Bakthin