Respuesta :
Answer:
Step-by-step explanation:
step 1. convert the total value into pennies, so $1.29 = 129 cents
step 2. let x = number of 18 cent stamps
step 3. then, the number of 15 cent stamps will be 3x - 4
step 4. our equation will be 18x + 15(3x - 4) = 129
step 5. expanding, we get 18x + 45x - 60 = 129
step 6. combining, we get 63x = 189
step 7. solving, x = 3 then number of 18 cent stamps
step 8. then 3x - 4 = 9 - 4 = 5 the number of 15 cent stamps
Proof: (18 x 3) + (15 x 5) = 54 + 75 = 129
Answer: there are 5 15 cents stamps in the drawer.
Step-by-step explanation:
The drawer contains 15 cents stamps and 18 cent stamps.
Let x represent the number of 15 cents stamps that is inside the drawer.
Let y represent the number of 18 cents stamps that is inside the drawer.
the number of 15 cent stamps is four less than three times the number of 18 cent stamps. This means that
x = 3y - 4
The total value of all the stamps is 1.29 dollars. Converting 1.29 dollars to cents, it becomes 1.29×100 = 129 cents.
Therefore
15x + 18y = 129 - - - - - - - - - - -1
Substituting x = 3y - 4 into equation 1, it becomes
15(3y - 4) + 18y = 129
45y - 60 + 18y = 129
45y + 18y = 129 + 60
63y = 189
y = 189/63 = 3
substituting y = 3 into x = 3y - 4, it becomes
x = 3×3 - 4 = 9-4 = 5
