Answer
b
Step-by-step explanation:
I see this as the difference in their current years is 12, and the difference between the number of years they both age in human years is 3, so after 4 human years they become the same age.
Plug in the second equation into the first equation for y.

Now put the variable on one side and constants on the other

Now plug that back into one of the original equations

So now you know

Its always a good idea to check
Answer: hold on
Step-by-step explanation:
4,000,006,400 in standard form