we know angle RLP= 100⁰
also
angle RLP+ angle RLB=180⁰(Linear pair)
=>100⁰+angleRLB= 180⁰
=> angle RLB=80⁰
since BR and LR are equal, angle RBL and angle RLB are equal
therefore angle RBL is also equal to 80⁰
using angle sum property of triangles we know that the sum of all angles in a triangle is equal to 180⁰
=>angle BRL+angle RBL+angle RLB= 180⁰
=> angle BRL+80⁰+80⁰=180⁰
=>angle BRL = 180⁰-160⁰
=>angle BRL= 20⁰
I'm sorry it took me some time I'm a slow typer