Answer:
Present ages:
Mouse is 3 years,
Owner is 10 years
Explanation:
Let m and o be the current ages of the pet mouse (m) and owner (o).
"Three years from now, a pet mouse will be as old as his owner was four years ago" can be written as:
(the mouse 3 years from now) (will be as old as) (his owner was four years ago)
(m + 3) = (o - 4)
Their present ages total 13 years.
m + o = 13 years
Find m and o.
(m + 3) = (o - 4)
m + o = 13 years
We have 2 equations and 2 unknowns. We should be able to find the answer through substitution.
Rearrange either equation so that one variable is isolate. Lets use the second:
m + o = 13 years(y)
m = (13 - o) [the unit for 13 is years]
Now use this definition of m in the first equation:
(m + 3) = (o - 4)
((13 - o) + 3) = (o - 4)
(16 - o) = (o - 4)
20 = 2o
o = 10 the owner is currently 10 years old.
Since m = (13 - o)
m = (13 - 10)
m = the mouse is currently 3 years old