ok i’ll try to help
split the prism into two rectangle, one 5ft by 3ft and one 3ft by 2ft
multiple 5 and 3 to find the area of the first rectangle
5x3=15
then multiple 3 and 2 to find the area of the second rectangle
3x2=6
add up 15 and 6 to find the area of the total figure
your answer should be 21
hope this helped!!