Answer:
The Subtraction equation use to find the age of his oldest relative is [tex]x-79=5[/tex].
Step-by-step explanation:
Given:
Age of youngest  relative = 5 years
We need to write a subtraction equation that could be used to find the age of his oldest relative.
Solution:
Let the age of the oldest relative be 'x'.
Now given:
Age of youngest  relative is 79 years less than the age of his oldest relative.
So we can say that;
Age of oldest relative minus 79 is equal to Age of the youngest relative.
framing in equation form we get;
[tex]x-79=5[/tex]
Hence the Subtraction equation use to find the age of his oldest relative is [tex]x-79=5[/tex].