Answer:
b = 55°
Step-by-step explanation:
Angles around a point will always add up to 360°
Therefore, we can write an expression where we sum the 3 angles given and equate them to 360°:
(b - 15) + 3b + (2b + 45) = 360
eliminate the brackets and collect like terms:
b + 3b + 2b - 15 + 45 = 360
Combine like terms:
6b + 30 = 360
subtract 30 from both sides:
6b = 330
divide both sides by 6:
6b ÷ 6 = 330 ÷ 6
⇒ b = 55
