Two ratios are proportional if after reducing them to thier lowest terms, they results are the same. By reducing to its lowest term, the numerator and denominator is divided by a common fraction until it cannot be reduced further.
For 20/35, if we divide the numerator and denominator by 5, it becomes
4/7
For 30/45, if we divide the numerator and denominator by 15, it becomes
2/3
Since the results are not equal, then the ratios are
