Does somebody know the answer? If you can please explain

None of them are correct.
You have to isolate the variable by dividing each side by factors that don't contain the variable.
And when you do so you get a closed point starting at positive 8 and an extending ray to positive infinity and a closed point at -15 with a ray extending to negative infinity on the number line so none of them are correct.

£5. This is because 50p is 10%. To get 100% you therefore need to times 50p by 10, thus getting £5