I could not understand what they meant by "solving (I) and (ii)". Could you please tell me ?
Let the other two angles be x and y
Given x−y=35∘...........(i)
Now using the angle sum property of the triangle
⇒x+y+75∘=180∘⇒x+y=105∘...........(ii)
Solving (i) and (ii)
x=70∘,y=35∘
So the measure of the largest angle is 75∘