4.85 is the answer because if you subtract 51.2 from 56.05 you get your answer
276400(0.035) = $9674 the equivalent value in dollar for every increase in the house then multiplied by 25. $9674*(25) = $241850 + the current value of Alex's home. $276400+ $241850 = $518250 that would be the value of Alex's home in 25 years. The percentage is (518250-276400)/ 276400 =0.875 *100 = 87.5 % increase in value. I hope this would help.
Answer:
There is no slope. 
Step-by-step explanation:

(2, 2) and (4,2) makes a horizontal line. All horizontal lines on a graph have no slope.