Answer:
30 of the 15 cent stamps and 50 of the 25 cent stamps
Step-by-step explanation:
Create a system of equations, where x is the number of 15 cent stamps and y is the number of 25 cent stamps:
x + y = 80
0.15x + 0.25y = 17
Solve by substitution by rearranging the first equation:
x + y = 80
x = 80 - y
Substitute 80 - y as x into the second equation:
0.15x + 0.25y = 17
0.15(80 - y) + 0.25y = 17
12 - 0.15y + 0.25y = 17
12 + 0.1y = 17
Solve for y:
0.1y = 5
y = 50
Plug in 50 as y into the first equation, and solve for x:
x + y = 80
x + 50 = 80
x = 30
So, you bought 30 of the 15 cent stamps and 50 of the 25 cent stamps
