SOLUTION: Brett is twice as old as his sister. four years ago he was four Times as old as his sister. how old is brett's sister now

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Question 919158: Brett is twice as old as his sister. four years ago he was four Times as old as his sister. how old is brett's sister now
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

let Brett's age be x
his sister’s age y
given:
Brett is twice as old as his sister.
x=2y .............1
four years ago he was four times as old as his sister
x-4=4%28y-4%29 .............2

solve the system:
x=2y .............1
x-4=4%28y-4%29 .............2
__________________________________substitute x from 1 in 2
2y-4=4%28y-4%29 .............2..solve for y
2y-4=4y-16
16-4=4y-2y
12=2y
12%2F2=y
highlight%28y=6%29...........his sister’s age now

x=2y .............1..plug in 6 for y
x=2%2A6
x=12 ...........Brett's age now