Jawabanmu

2014-08-17T20:35:03+07:00
30/(30-10) = 60/((60-5)-a)
30/20 = 60/55-a
1650-30a = 1200
450 = 30a
a = 450/30
a = 15 cm (lebar)
panjangnya 30-10 = 20 cm
ukuran fotonya 20cm x 15 cm