Final Answer is 4.5
= 4.5hours more time was used on games than on research.
The rate of change would be D. 4
During week 2, he could type 15 words per minute, at his fourth week, he could type 30. So 30-15=15. He could type 15 words faster on week 4 than he could at week 2.
X= 9 over 4 is the correct answer