Find the y value for point i such that di and ei form a 3: 5 ratio

X value for the point I is x = 0 ( we will use the similarity of triangles: from the point D goes the line that is perpendicular to y-axis and forms the right triangle with the line from the point E that is perpendicular on the x-axis; those segments also form a ratio 3: 5 )
After that we can find the length of the line DE:
DE =√ ( 8² + 3²) = √ 73 = 8.544
DI = ( 8.544 : 8 ) · 3 = 3.20775  
n - the distance between the line from the point D and the point I:
n² = 3.20775² - 3² = 10.28966 - 9 = 1.28966
n = √ 1.28966 ≈ 1.15
y = 2 + 1.15
y = 3.15
A)