Final answer:
By subtracting the amount of blue paint, 4.5 pints, from the total amount of paint, 7.8 pints, it is determined that Sean used 3.3 pints of white paint.
Step-by-step explanation:
Sean used a total of 7.8 pints of paint, with 4.5 pints being blue paint. To find the amount of white paint used, we have to subtract the amount of blue paint from the total amount of paint. So, we calculate 7.8 pints - 4.5 pints.
The calculation is:
7.8 pints (total paint) - 4.5 pints (blue paint) = 3.3 pints
Therefore, Sean used 3.3 pints of white paint to paint his bedroom walls.