Final answer:
The equivalent equation to m = ca is B) a equals m over c, obtained by isolating 'a' through division by 'c'.
Step-by-step explanation:
The original equation given is m = ca. To find an equivalent equation, we must isolate 'a' in the equation. We can divide both sides by 'c' to isolate 'a' on one side. The result is a = m / c, which is equivalent to the original equation. Therefore, the equivalent equation to m = ca is B) a equals m over c. This process is similar to using a conversion factor in unit conversion, where we ensure the original unit cancels out to convert to the desired unit, as shown in the given example where quantities expressed in different units are set equal to maintain an equality.