This is not impossible :/ step 1- multiply 5 by 2 since each pound is 2 dollars then you get 10 now find 20% of 10 so multiply 10 by .20 and you get 200 move the decimal to times to the left so you get $2.00 so thats 20% of $10 so subtract 2.00 by 10.00 and the new total cost is $8.00… .