Answer:
$18,000
Step-by-step explanation:
If Lindsey’s college will cost her a total of $6,000 a year, for the next three years the total cost will be 3×$6,000 which gives $18,000.
Note that she is only foregoing making $26,000 a year at the local mall therefore if she doesn't work at all, she won't make any money but will keep paying for her college fee.
Her total investment in education if she doesn't work at all and finishes in 3 years will remain the amount she paid for 3years in college which is $18000