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.
All you have to do is substitute the y, which is 5, and the x, which is 2, into the equation. When you solve it the answer in the end will be 5=5, which means that point (2,5) does line on that line.