9, 2, -5... so is going down by 7 each time, meaning the "common difference" is -7.
If you would like to write 0.423 as a percent, you can calculate this using the following step:
0.423 * 100% = 42.3%
The correct result would be 42.3%.
Answer:
9 sleeves for 22.99
Step-by-step explanation
The first pack has a unit rate of $11.49/ 4 balls
=$2.8725
The second pack has a unit rate of $16.79/6balls
=$2.798 per ball
the third pack has a unit rate of $22.99/9balls
=2.554
So, I would definitely go for the third pack since it has the least cost.