Angle EBC=3r+10

Angle ABE=2r-20

Find angle EBF

Solution:

The angles EBC & ABE form a linear pair.

So, ∠EBC + ∠ABE = 180

3r+10+2r-20 = 180

5r-10=180

5r=180+10

5r=190

r=190/5

r=38

Substitude

Since, ∠EBF = ∠ABE

∠EBF = 2r-20

∠EBF = 2 (38) - 20

∠EBF=76-20

∠EBF=56 (Answer)