Find the value of a pronumeral in linear and simple non-linear equations given the values of the other pronumerals, transposing equations where necessary.

A mobile phone plan charges a base fee of $\$B$ per month plus $\$0.15$ per minute of calls. The total monthly cost is given by the formula $C = B + 0.15m$, where $m$ is the number of minutes used. If the total monthly cost was $\$47.50$ and the customer used $180$ minutes, which expression correctly gives the base fee $B$?

The volume of a rectangular prism is given by the formula $V = l \times w \times h$, where $l$ is length, $w$ is width, and $h$ is height, all measured in centimetres. A storage box has volume $6{,}000 \text{ cm}^3$, length $50 \text{ cm}$ and width $40 \text{ cm}$. Find the height of the storage box.