Question

Farida bought 20 stamps consisting of 20 sen stamps and 60 sen stamps. The total cost of the stamps is RM8.80. How many 20 sej stamps did Farida buy?

Answer 1

Answer:

# of 20cent stamps = 8

Step-by-step explanation:

Let the  number 20cent stamps be = x

Let the number 60 cents stamps be = y

Total number of stamps => 20 = x + y ----------- ( 1 )

Total cost of the stamps = 8.80

That is, 0.20x + 0.60y = 8.80 ------------- ( 2 )

      ( 2 ) => 20x + 60y = 880

            => x + 3y = 44

           =>  x = 44 - 3y

Substitute x in  ( 1 ) => x  +  y = 20

                                 44 - 3y + y = 20

                                     - 2y = 20 - 44

                                     - 2y = - 24

                                       2y = 24

                                       y = 12

Substitute y = 12 in  ( 1 ) => x + y = 20

                                         x + 12 = 20

                                            x = 8