Let x be the number of cookies purchased.
(1) Jane bought x cookies that were $3 each
[tex]3x=\text{total spent by Jane}[/tex](2) John bought x cookies $1 each and a small cake for $10
[tex]1\cdot x+10=\text{total spent by John}[/tex]Since they spent the same amount of money, we can equalize the expressions:
[tex]\begin{gathered} 3x=x+10 \\ \end{gathered}[/tex]Solve for x:
[tex]\begin{gathered} 3x-x=10 \\ 2x=10 \\ x=\frac{10}{2} \\ x=5 \end{gathered}[/tex]They purchased 5 cookies.
The equation that represents the situation is:
3x=x+10
