(0,2.5)(4,2.5)...u will notice that the y's are the same.....that means this is a horizontal line and y will always be 2.5.
so u want a perpendicular line...going through (3,-1)...a perpendicular line would be a vertical line...and a vertical line is represented by x = a number...so look at ur points (3,-1)....what number is in the x spot ? It is 3.....so ur perpendicular line is : x = 3
