SOLUTION: This entire lesson revolves around the 3 step principle of: assigning a variable writing a sentence placing the demands on the variable solving the equation. We need a usable f

Question 125029: This entire lesson revolves around the 3 step principle of:
assigning a variable
writing a sentence placing the demands on the variable
solving the equation.
We need a usable formula that will work in all these cases!
THANK YOU!!!
Here's the question:
Two years ago a father was four times as old as his son. Three years from now the father will be only three times as old as the son. How old is each now?
Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
Define the variables any way you want, as long as you are consistent, and then solve the equation. The one that works best with your brain is the best for you. This one is best for mine:
.
Let x be the son's age 2 yrs ago.
Let y be the father's age 2 yrs ago.
Both these variables are consistent (2 yrs ago). You could have made them equal to the present or three yrs from now. You would have had different equations in those cases but the answers (if ou did it right) would have been the same.
.
A) y=4x 2 yrs ago
B) y+5=3(x+5) 3 yrs from now.
.
Substitute 4x for y in B):
4x+5=3x+15
4x-3x+5-5=3x-3x+15-5
x=10
A) y=4*10
y=40
.
So the son is now 12 and the father 42.
.
Ed

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