Answer: 18th year In this question, the income is increasing each year with the same amount, first-year income is $20,400 and 11th-year income is $31,400. From this information, you can determine how much the income increases every year. The calculation would be:
Income year Y= first income + {(Y-1) * income increase per year )} $31,400= $20,400 + 10 * income increase per year 10* income increase per year= $11000 income increase per year= $1100
Using the same formula you can find the answer
Income year Y= first income + {(Y-1) * income increase per year )} $40,200= $20,400 + Y* 1100 1100Y= 40,200-20,400= 19800 Y= 19800/1100= 18 year.