[tex]denote \: by \: s \: the \: cost \: of \: a \: sweatshirt \\ denote \: by \: t \: the \: cost \: of \: a \: t \: shirt[/tex]
[tex]3t + 7s = 240.5 \\ 6t + 5s = 220[/tex]
[tex] - 6t - 14s = - 481 \\ 6t + 5s = 220[/tex]
[tex] - 9s = - 261 \\ s = \frac{ - 261}{ - 9} = 29 \: dollars[/tex]
[tex]3t + 7(29) = 240.5 \\ [/tex]
3t + 203 = 240.5
3t = 37.5
t = 12.5 dollars