Answer:
48 degrees
Step-by-step explanation:
Perhaps I'm wrong, but if you understand that the entire ∠CBA forms 160 degrees, and the ∠RBA forms 112 degrees OUT of that same 160 degrees, then ∠RBC (which looks the same as m∠4?) must therefore be equivalent to 48 degrees, given 112+48 = 160 degrees.
