y=1800*1.05^x. Since the fund grows at an annual rate of 5%, each year it will be (1+5%) or (1.05) times in value the year before. Therefore, the fund after first year will be 1800*1.05, the second year will be 1800*1.05*1.05,... after x years, the value will be 1800*(1.05)^x dollars.