At the start of lunch Jimmy and Jake each brought out a new bag of $x$ marbles to play with their friends. By the end of lunch they were surprised to see they still had the same number as each other even though overall Jimmy had gained $5$ marbles and Jake had ended up with the double of $3$ less than his original amount. How many marbles were originally in the bags?
My attempt
$2x=(x+5)+2(x-3)$
$x=1$
The correct solution is $11$ marbles
Jimmy end up gaining $5$: $x+5$
Jack end up with double of $3$ less than original amount. $2(x-3)$
$$x+5=2(x-3)$$
Note that they have other friends to gain or lose from, hence both of them gain additional marbles. The question doesn't mean their sum stays the same.