Sona had $55 at the beginning of the day. She went to the museum and spent $12.75 on her ticket and $8.50 on a t-shirt. She then bought lunch for $9.32 and got a treat for $1.78. Last, Sona went to a store and bought three notebooks each for $3.32 and two packs of pens for $4.50 each.
How much money did Sona have left at the end of the day?
Sona spent 12.75 + 8.50 + 9.32 + 1.78 = $<<12.75+8.50+9.32+1.78=32.35>>32.35 on museum tickets, t-shirt, lunch, and a treat.
She spent 3.32 x 3 = $<<3.32*3=9.96>>9.96 on notebooks.
She spent 4.50 x 2 = $<<4.50*2=9.00>>9.00 on pens.
She spent 32.35 + 9.96 + 9 = $<<32.35+9.96+9=51.31>>51.31 in total.
Sona has 55 - 51.31 = $<<55-51.31=3.6699999999999875>>3.67 left. Answer: \boxed{3.67}.