Answer:
Number of 13 cents stamp = 14
Number of 29 cents stamp = 24
Number of 45 cents stamp = 16
Step-by-step explanation:
We are told he has 54 stamps in total.
These stamps are;13 cent, 29 cent, and 45 cent stamps.
Let's call number of 13 cent($0.13) stamp A
Call number of 29 cent($0.29) stamp B
Call number of 45 cent($0.45) stamp C
Thus;
A + B + C = 54
We are told the total value of the 3 stamps are $15.98.
Thus;
0.13A + 0.29B + 0.45C = $15.98 - - - (eq2)
Now we are told that if the number of 13 cent stamps is doubled, the new total value of his stamp collection would be $17.80.
Thus;
2(0.13A) + 0.29B + 0.45C = 17.8
0.26A + 0.29B + 0.45C = 17.8 - - - (eq 3)
Solving the 3 equations simultaneously, we have;
A = 14
B = 24
C = 16
We have;
Number of 13 cents stamp = 14
Number of 29 cents stamp = 24
Number of 45 cents stamp = 16