Since Bryan spent $15.50 less than Sarah, you would start by dividing the total amount they spent together in half.
$47.50 ÷ 2 = $23.75
Then you would take Bryan's 1/2 of the total and subtract $15.50.
$23.75 - $15.50 = $8.25
So, it looks like Bryan spent $8.25.
Check step:
If you add it all back together:
Sarah + Sarah Bryan = Total
$23.75 + $15.50 + $8.25 = $47.50
