Setting up the equation:
The given equation is:
\[ 88000 - 1200t = 42000 + 800t \]
Step 1: Bring like terms together:
\[ 88000 - 42000 = 1200t + 800t \]
Step 2: Simplify the equation:
\[ 46000 = 2000t \]
Step 3: Solve for \( t \):
\[ t = \frac{46000}{2000} = 23 \text{ years} \]
Thus, the correct answer is 23 years.