The image is blurry and is hard to make out what the number for width is. However you can find the proportionality factor between the phones by dividing the large phone height by the small phone height. So 6.21in/5.4in, you get 1.15in, this means that the larger phone is 1.15in bigger than the smaller phone. Apply this number to the width and you will find the width of the larger phone since both phones are proportional. So you do width × 1.15 to get the width of the larger phone.
