1. The problem is to rearrange the formula $h = a v$ to make $a$ the subject. 2. Start with the equation: $$h = a v$$ 3. To isolate $a$, divide both sides of the equation by $v$ (assuming $v \neq 0$): $$\frac{h}{v} = \frac{a v}{v}$$ 4. Simplify the right side: $$\frac{h}{v} = a$$ 5. Therefore, the subject $a$ is: $$a = \frac{h}{v}$$ This means $a$ is equal to $h$ divided by $v$.