SOLUTION: How do I solve by using two equations in two variables? Larry is 8 years older than his sister. In 3 years, he will be twice as old as she is now. How old are they now?

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Question 141367This question is from textbook Prentice hall algebra 1
: How do I solve by using two equations in two variables?
Larry is 8 years older than his sister. In 3 years, he will be twice as old as she is now. How old are they now? This question is from textbook Prentice hall algebra 1

Answer by ptaylor(2198) About Me  (Show Source):
You can put this solution on YOUR website!

Let x=sister's age
And let y=Larry's age
y+3=Larry's age 3 years from now
Now we are told the following:
y=x+8------------------------------------eq1
and
y+3=2x-----------------------------------eq2
substitute y=x+3 from eq1 into eq2
x+8+3=2x subtract x from each side
x-x+8+3=2x-x collect like terms
11=x or
x=11-------------------------------sister's age now
substitute into eq1
y=11+8=19----------------------------Larry's age now
CK
19 is 8 years older than 11
and
22=2*11
22=22

Hope this helps---ptaylor