Film A is 30 minutes longer than Film B, Film C is twice as long as Film B. All 3 films have a total run time of 390 minutes. How long is each film?

The first step is to express each bit of information as an algebraic equation and then manipulate them so we are only using one letter. 'Film A is 30 minutes longer than Film B' can make the equation: A= B + 30, 'Film C is twice as long as Film B' can make the equation: C = 2B ', All 3 films have a total run time of 390 minutes' can make the equation A + B + C = 390. By rearranging the equations so that we are only involving B the equation can be solved: B + 30 + B + 2B = 390 This simplifies to 4B + 30 = 390 4B = 360 (minus 30 from both sides), then B = 90 (divide both sides by 4). This answer can then be substituted back into the earlier equation to work the length of Film A (120 mins) and Film C (180 mins)