In the given question, there are several important information's provided. using these information's the required answer can be easily deduced. It is given that Joe spends 50% of his pocket money first and then another 1.50 pound. After that hoe has 75p left.
Let us assume that the amount of pocket money Joe has = x
Then
(x/2) + 1.50 +0.75 = x
x + 3.0 + 1.5 = 2x
2x - x = 4.5
x = 4.5
So the amount of money Joe has as his pocket money is 4.5 pounds