posted by D .
Well, hard to imagine the picture, but by the description the wires each side are at 16 deg. back on each side of the tooth, i.e. each at 16 deg. to the face of the tooth. Each has 18N. tension.
(sin 16) x 18 = 4.9608N.
Double it (2 wires), = 9.9216N. back on the tooth.