Julie gave away 15 pieces.
I found my answer by making an equation. For Julies half, we do 20-x because we don't know how many pieces she gave away but we do know how many pieces she started with. For Conrads half, we do 35-2x because we know he started out with 35 pieces and gave away two times how much Julie gave away so 2x. Then because we want them to have the same amount of gum left we set their two halves as equal to eachother.
So our equation is 20-x=35-2x. Then we solve:
20-x=35-2x (then we subtract 20 from both sides to move it right)
-x=15-2x (then we add 2x to both sides to move it left)
x=15 (and here is out answer)
