Let:
x = pieces of pizza eaten by Daniel
y = Pieces of pizza eaten by Jeremy
Daniel ate 3 pieces of pizza. so:
[tex]x=3[/tex]Jeremy ate 2 times that much, so:
[tex]\begin{gathered} y=2x \\ so\colon \\ y=2(3) \\ y=6 \end{gathered}[/tex]Jeremy ate 6 pieces of pizza