<em>r</em> should be 4/7. You're comparing the given series to a geometric series that converges. By the limit comparison test, you have
and since this limit is positive and finite, and the series you're comparing to is convergent, then the first series must also be convergent.
Well the angle is acute at the 3 it would be a right angle so I'm guessing it's 30 degrees but if I'm wrong u could use a protractor to find the angle of degrees
1a+18=7a
18=7a-1a
18=6a
6a=18
a=18/6
a=3