measure of angle B= 110ft² = 20ft² + 120ft² - 2(110)(20)cosB
Then you can find angle a with...
180 - (angleB + angleC)
Gster's way is much simpler lol.
"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man."
George Bernard Shaw - Man and Superman