Answer:
10 years old
Explanation:
Let m = mother's age
Let f = father's age
Let d = Dina's age
m = 4d d = f-35 f = m+5
Substitute the middle equation in to the first equation
m = 4(f - 35) Use the distributive property
m = 4f - 140 subtract 4f from both sides
*m -4f = -140
In equation 3 above, subtract m from both sides to get
f = m+5
f - m = 5 rearrange so that the m term is first
*-m + f = 5
Now add the equations together that have *
m -4f = -140
-m + f = 5
-3f = -135 Divide both sides by -3
f = 45 This is the father's age. To find Dina's age, plug 45 into the second equation above:
d = f -35
d = 45 -35
d = 10.
To find the mom's age, use the third equation:
f = m+5
45 = m + 5
40 = m
You can check this by plugging the answers you found and you can see that all three equations are solved.
m = 4d d = f - 35 f = m + 5
40 = 4(10) 10 = 45 - 35 45 = 40 + 5
40 = 40 10 = 10 45 = 45