How can i simplify this if sequence?

I am learning java, and i got stuck in a stupid situation.

I could just throw all my code in here, but it would only confuse you even more. So I converted my logical thinking into this:

if (a) { instruction 1 }

if (!a && b && !c) { instruction 2 }

if (!a && b && c) { instruction 3 } else { instruction 4 }

All I want to know is if i can simplify this, so i don't use so many "if" statements... And I'd like to know how you came to your conclusion.

Thanks in advance! (Yes, I'm dumb, help me)