One day, a girl bought 20 first-class stamps and 10 postcard stamps for $17.10. Another day she spent $70.70 on 80 first-class stamps and 50 postcard stamps. Find the cost of each type of stamp.

$0.775

Step-by-step explanation:

Let x represent the cost of 1st class stamps

Let y represent the cost of post card stamps

17.10 = 20x + 10y (1)

70.00 = 80x + 50y (2)

subtracting 4 of equation 1 from equation 2 you obtain the following:

1.6 = 10y

which gives y = .16

Therefore post card stamps cost $0.16

Plugging this back into either equation you get x = .775

Therefore the cost of 1st class stamps is $0.775

8+10

step-by-step explanation:

you multiply 4 by 2 and 5 by 2