Your not stupid, you just don't know everything yet and guess when you know everything....never. but you.ll get better.
Angles across from each other like 7 and 5 are called vertical angles and they are the same (92)
angles beside each other are called linear pairs and if you add them together then are 180. so 5 + 8 = 180 and 5 is 92 so
92 + ∠8 = 180
∠8 = 180 -92 = 88
