PLEASE HEEEELPPPP I WILL GIVE BRAINLIEST

Answer:
3
Step-by-step explanation:
If you pay attention closely you will see that side 5 and side x look relatively similar. Now if we look at our options we see 7.5 which is too big, 45 which is way too big to be our answer, 8 which has gotten too big and 3 which is similar to 5. This means we have our answer!