Answer: 10.6 years
Step-by-step explanation:
The current salary is $42k per year
the college degree cost $28k per year, and with the degree he can win $56k per year, and here we also can consider that he "loses" the $42k tat he would have earned if he keeped working.
Then, the amount of money per year is:
m1(y) = $42k*y
m2(y) = -2*$42k - 2*$28k + $56k*y
where y is the number of years after he gets his degree,
Now, we must find the value of y where those equations are equal:
$42k*y = -2*$42k - 2*$28k + $56k*y = -2*($28k + $42k) + $56k*y
($42k - $56k)*y = -2*$60k = -$120k
y = 120k/14k = 8.6 years
but remember that we coun y after he gets his degree, which takes 2 years, so the actual number of years that he needs to recover his inversion is (8.6 +2) years = 10.6 years
