Jack bought 34 stamps at the post office. red stamps were $0.33 each and the blue stamps were $0.50 each. if the total cost of the stamps was 12.75,how many of each type did he buy?

Let r = red stamps
And b= blue stamps

r+b=34
0.33r+0.5b=12.75

Solve by substitution, isolate the variable r
r=-b+34
Substitute into second equation
0.33(-b+34)+0.5b=12.75
Distribute
-0.33b+11.22+0.5b=12.75
Collect like terms and isolate the variable
0.17b=1.53
Divide by 0.17
b=9

Subtract from 34 to get the number of red stamps
34-9=25

He brought 9 blue stamps and 25 red stamps

Hope i can you!