Think about it this way, what is 5x3??? 15 right. Ok then what is 5x30???? 150. So the store should sell each soccer ball for $5 each:)
If we assume that Jane spent $ x on the black pack
Then the cost of the book is $ 20 less that twice the cos of the black pack,
Then twice the cost of black pack is 2x, then less $ 20 we get 2x-20
Hence , 60 =2x-20
solving for x
x = 40
Therefore, the cost of the black pack is $40.
