Is b perpendicular to a? Justify your answer.

Set up the equation: 2x+37+3x+y=180 ⇒ 4x+y=143
2x+y+3y-21=180 ⇒2x+4y=201.
Solving for x and y, you get that y=37, thus making x=26.5
Now, for b to be perpendicular to a, 2x+37 must equal 90.
2*26.5+37=90, so b is perpendicular to a.