Respuesta :
Answer:
set mary is x years old, and helen is y years old.
first sentence:x=2y
second one:4(y-8)=x+4
bring x=2y in 4(y-8)=x+4
=>4y-32=2y+4
=>2y=36
=>y=18
=>x=36
mary:36
helen:18
We want to write and solve a system of equations that models given situation. We will see that Helen is 18 years old, and Mary is 36 years old.
Let's define the variables we will be using.
- m = Mary's age.
- h = Helen's age.
We know that "Mary is twice as old as Helen’s age"
Then:
m = 2*h
"If 8 is subtracted from Helen’s Age and 4 is added to Mary Age, Mary will be 4 times as old as Helen."
(m + 4) = 4*(h - 8)
Then the system of equations is:
m = 2*h
(m + 4) = 4*(h - 8)
To solve it, we can replace m by 2*h in the second equation, so we get:
(2h + 4) = 4*(h - 8)
2*h + 4 = 4*h - 32
4 + 32 = 4*h - 2*h
36/2 = h = 18
And we know that:
m = 2*h = 2*18 = 36
So Helen is 18 years old, and Mary is 36 years old.
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