In 5 years, Dad will be three times as old as his daughter Jill will be then. If the sum of their present ages is 50, how old are they now?
If x + 5 is Jill's age five years from now, which of the following equations could be used to solve the problem?
a.3x + 5 = 55 - x
b.3x + 15 = 55 - x
c.3x + 15 = 45 - x ...?
In 5 years, Dad will be three times as old as his daughter Jill will be then: y + 5 = 3(x + 5)
The sum of their present ages is 50: x + y = 50
We have the system of two equations now: y + 5 = 3(x + 5) x + y = 50
Let's rearrange the second equation: If: x + y = 50 Then: y = 50 - x
Now, substitute y from the second equation (y = 50 - x) into the first one: y + 5 = 3(x + 5) 50 - x + 5 = 3(x + 5) 50 + 5 - x = 3*x + 3*5 55 - x = 3x + 15
Rearrange it a bit: 3x + 15 = 55 - x Therefore, the correct choice is b.
