<span>Sarah's conclusion is invalid, because she is testing two variables at once without a control value. In order for the experiment to be valid, Sarah should either apply the same soil to both areas (assuming they are, in fact, the same). Or, she should water both equally. At this time, we don't know if B grew "better" due to the brand or the amount of water received.</span>
Step-by-step explanation:
4 times = 4x increased by 7 = 4x+7
