math yth grader

Question

yumma has 31 paintings to sell. he sells 2 paintings every 3 days. Determaine how many days until yumma has 19 paintings left.

Answer 1

31

in 3 days 29

in 6 days 27

in 9 days 25

in 12 days 23

in 15 days 21

in 18 days 19

in 18 days he'll be down to 19 paintings

2 less paintings every 3 days means P=-2D/3 + 32

P= 32 - (2/3)D

where P = number of paintings and D = days

19=32 -2D/3

2D/3 = 32-19 = 13

D = (3/2)(13) = 39/2 = 18 days