There are 495 coins in a bottle. 1/3 of the coins are £1 coins. 124 of the coins are 50p coins. The rest of the coins are 20p coins. Work out the total value of the 495 coins

495/3 = 165 => £165 worth of £1 coins
124 x 0.5 = 62 => £62 worth of 50p coins
We know the number of coins that are NOT 20p coins. Therefore, we can subtract the number of non-20p coins from the total number of coins to figure out how many 20p coins we have. 495 - 165 - 124 = 206 206 x 0.2 = 41.2 => £41.2 worth of 20p
Now we add up the values we figured out:165 + 62 + 41.2 = £268.2