Simple interest:
54000 x 0.038 x (3/12) =
i don't know what i'm doing wrong

The simple interest rate equation is I = Prt
I = interest
P = principle ($54,000)
r = rate (3.875%)
t = time (3 months, so .25 years)

I = Prt
I = (54,000)*(.03875)*(.25)
I = $523.125

I = Prt
I = 54000*.03875*3
54000 is the principal
.00875 is the same thing as 3+(7/8) %, because to make a decimal a percentage you multiply by 100
3 is the time
I = 6277.5
That's the amount that has been made off of interest alone. If you're looking for the total amount of money, it's 54000+6277.5=60277.5

That she received $100