Why Ohm's Law says voltage equals current multiplied by resistance, E = I x R, where E is in volts, I in amperes and R in ohms. Push more current through the same resistance and the voltage drop rises proportionally; raise the resistance at the same current and the voltage rises too. The same relationship rearranges to I = E / R and R = E / I, so knowing one form gives you all three.
Watch out Dividing current by resistance is just Ohm's Law scrambled, and the forms with I squared come from the power formula P = I squared x R, which gives watts, not volts.
Cover the letter you want in the E over I R triangle: E is on top, so E = I x R.