Summing fractions the wrong way

Algebra Level 2

You should know that

$\frac{a}{b} + \frac{c}{d} \ne \frac{a+c}{b+d}.$

However, if $a, b, c, d$ are positive integers that satisfy $\frac{a}{b} < \frac{c}{d},$ what can we say about $\frac{a+c}{b+d} ?$