Inside of the triangle must = 180. Let angle '4' = x. x + 45 + 47 = 180. Combine like terms, x + 92 = 180. Subtract 92 on both sides, x = 88.
Now angle '4' and angle '3' must equal 180 because they are on the same plane. Let angle '3' = y. y + 88 = 180. Subtract 88 on both sides, y = 92.
So Angle 4 is 88 degrees and Angle 3 is 92 degrees.
