we can solve this problem by trial and error method 
we are given costs of each items
Chocolate - £1
Cinema Tkt - £5
Mobile TopUp - £10
Pizza - £6
Let's assume we take each one item 
chocolate+cinema ticket +mobile top up+pizza 

and we have total £25
so, remaining sum 

so, with this money , we can only buy chocolate
so, number of chocolate is 4
number of cinema ticket is 1
number of mobile top up is 1
number of pizza is 1
now, we can find fraction of money spent on each from savings 
so, we 
spent money on Chocolate =1*4=£4 
money spent on cinema ticket is £5
money spent on Mobile Top Up is £10
money spent on Pizza is £6