## Explanation

### Evaluating 3/8 = 15/40

$\frac{3}{8} = \frac{15}{40}$Cross-multiply to verify:

$3 \times 40 = 120$ $8 \times 15 = 120$Since both cross-products are equal, **this proportion is true.**

### Evaluating 12/13 = 2/3

$\frac{12}{13} = \frac{2}{3}$Cross-multiply to verify:

$12 \times 3 = 36$ $13 \times 2 = 26$The cross-products are not equal, so **this proportion is not true.**

### Evaluating 9/13 = 27/36

$\frac{9}{13} = \frac{27}{36}$Cross-multiply to verify:

$9 \times 36 = 324$ $13 \times 27 = 351$The cross-products are not equal, so **this proportion is not true.**

### Evaluating 16/49 = 4/7

$\frac{16}{49} = \frac{4}{7}$Cross-multiply to verify:

$16 \times 7 = 112$ $49 \times 4 = 196$The cross-products are not equal, so **this proportion is not true.**

### Conclusion

The only true proportion among the given examples is:

$\frac{3}{8} = \frac{15}{40}$