Ans: 55°
Let's draw two parallel line intersecting angle x° and 45° as shown in the photo.
i) a=25° [Being Alternative Angle]
ii) d=15° [Being Alternative Angle]
iii) c= 45°-d[45°=c+d]
 =45°-15°
 =30°
iv)b=c[Being Alternative Angle]
v)x=a+b[Combining Angle a & b] 
 =25°+30°
 =55°