Answer:
24cm
Step-by-step explanation:
The photo stays the same, the card changes. They must be proportional to each other.
15 by x cm means the 30 is going to be shortened, since it is being cut.
16 / 10 = 1.6
1.6 x 30 = 24
    or
[tex]\frac{16}{10} = \frac{x}{15} \\\\Divide\\\\\frac{16}{10} *\frac{15}{x} = \frac{240}{10x} = 24[/tex]