Bob buys 33 pens and 21 rulers for £6. A ruler costs 8 pence more than a pen. How much does one pen cost?

Let the cost of a pen = xLet the cost of a ruler = x+8Thus, (x*33) + ((x+8)*21) = £6 = 600 penceHence, 33x + 21x + 168 = 600 54x = 432 x = 8Therefore one pen costs 8 pence.