[tex]1.\\x-how\ many\ biscuits\ has\ Gemma\\ \\x+4x=20\ \ \ \Leftrightarrow\ \ \ 5x=20\ \ \ \Leftrightarrow\ \ \ x=4\ \ \ \Rightarrow\ \ \ 4x=16\\ \\Ans.\ Gemma\ has\ 4\ biscuits\ and\ Zak\ has\ 16\ biscuits.[/tex]
[tex]2.\\x-how\ many\ marbles\ has\ Asif\\ \\7x+x=80\ \ \ \Leftrightarrow\ \ \ 8x=80\ \ \ \Leftrightarrow\ \ \ x=10\ \ \ \Rightarrow\ \ \ 7x=70\\ \\Ans.\ Asif\ has\ 10\ marbles\ and\ Emily\ has\ 70\ marbles.[/tex]
[tex]3.\\2x-how\ many\ pencils\ has\ Niamh\\ \\2x+3x=10\ \ \ \Leftrightarrow\ \ \ 5x=10\ \ \ \Leftrightarrow\ \ \ x=2\ \ \ \Rightarrow\ \ \ 2x=4\ \ and\ \ 3x=6\\ \\Ans.\ Niamh\ has\ 4\ pencils\ and\ Jack\ has\ 6\ pencils.[/tex]