$I = P\,r\,t$ is one fact wearing four outfits — solve it for $I$, $P$, $r$ or $t$ and it answers four different exam questions. The ladder never changes: pick the formula, rearrange it for what you want, load the numbers into their sockets, and only then compute.

One golden habit before the sockets: the formula wants $r$ as a decimal. Percent means per hundred, so 3% is $\tfrac{3}{100} = 0.03$ — slide the point two places left. Feed the formula a naked 3 instead and every answer comes out a hundred times too proud. This lesson will offer you that mistake on purpose, more than once. Decline politely.