Nevermind, I solved it.
For anyone else who has a similar problem I recommend using a tilted coordinate axis where the positive x direction is parallel to the direction of acceleration.
Homework Statement
A child is flying a large kite of mass 6.8 kg on a windy day. At the moment shown the tension from the string on the kite has a magnitude of 17.0 N and makes an angle of = 32.6° from the vertical, and the acceleration of the kite has a magnitude of ak = 7.72 m/s2 and makes...