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Doug have 30 quarters and 15 dimes.

Step-by-step explanation:

Given,

Number of coins = 45

Worth of coins = $9.00 = 9.00*100 = 900 cents

Each quarter = 25 cents

Each dime = 10 cents

Let,

x be the number of quarters

y be the number of dimes

According to given statement;

x+y=45            Eqn 1

25x+10y=900   Eqn 2

Multiplying Eqn 1 by 10

[tex]10(x+y=45)\\10x+10y=450\ \ \ Eqn\ 3[/tex]

Subtracting Eqn 3 from Eqn 2

[tex](25x+10y)-(10x+10y)=900-450\\25x+10y-10x-10y=450\\15x=450[/tex]

Dividing both sides by 15

[tex]\frac{15x}{15}=\frac{450}{15}\\x=30[/tex]

Putting x=30 in Eqn 1

[tex]30+y=45\\y=45-30\\y=15[/tex]

Doug have 30 quarters and 15 dimes.

Keywords: linear equation, elimination method

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Doug has 30 quarters and 15 dimes.

Let

x = number of quarters

y = number of dimes

The total number of coins is 45. Therefore,

Total number of coins:

  • x + y = 45

Total amount of the coins is $9. Therefore,

Total cost of the coins:

  • 0.25x + 0.1y = 9

Therefore,

x + y = 45

0.25x + 0.1y = 9

0.1x + 0.1y = 4.5

0.25x + 0.1y = 9

0.15x = 4.5

x = 4.5 / 0.15

x = 30

y = 45 - 30

y = 15

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