This is one way to solve the Brain Teaser.

Lee has a 10 on her shirt. (Two hands have 10 fingers.)
Max has a 6 on his shirt. (10 – 4 = 6)
Bud has a 16 on his shirt. (10 + 6 = 16)
Jan has a 12 on her shirt. (6 x 2 = 12)
Tara has a 13 on her shirt. (13 is the only number left)