How do you solve this?!!

Answer:
135°
Step-by-step explanation:
Step 1:
100° + 35° + 180° - ? = 180° Sum of a Δ/Vertical ∠'s
Step 2:
315° - ? = 180° Combine Like Terms
Step 3:
315° = 180° + ? Add ? on both sides
Step 4:
315° - 180° = ? Subtract
Answer:
? = 135°
Hope This Helps :)