When money is invested at 4.5% simple interest for 4 months, the interest is $105. Find the principal

Use the equation to find principal. P = A / (1+r/n) ^ (n) (t)

A = 105

r = 0.045 (remember you have to change percentage to a decimal)

n=12 (there are 12 months in a year)

t = 4 (number of months)

Plug this into your calculator

105 / (1 + 0.045/12) ^ (12) (4)