She has 40 coins all made up of quarters and dimes, And when she counted them up she had $7.75 from them, how much of each did she have?

x = number of quarters = 25

y = number of dimes = 15

Step-by-step explanation:

Let

x = number of quarters

y = number of dimes

1 dime = $0.10

1 quarter = $0.25

x + y = 40 (1)

0.25x + 0.10y = 7.75 (2)

From (1)

x = 40 - y

Substitute x = 40 - y into (2)

0.25x + 0.10y = 7.75 (2)

0.25(40 - y) + 0.10y = 7.75

10 - 0.25y + 0.10y = 7.75

- 0.25y + 0.10y = 7.75 - 10

-0.15y = -2.25

y = -2.25/-0.15

y = 15

Substitute y = 15 into (1)

x + y = 40 (1)

x + 15 = 40

x = 40 - 15

x = 25

x = number of quarters = 25

y = number of dimes = 15

Total quarters = 25 × $0.25

= $6.25

Total dimes = 15 × $0.10

= $1.5

f

step-by-step explanation:

f

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.