hello,
the first term is 250 so this is the initial invested amount
[tex](1+\dfrac{0.08}{12})^{12}=(1+\dfrac{8\%}{12})^{12}[/tex]
is to compute 8% annual interest compounded monthly (there are 12 months in a year)
and then multiply by 4 means that it is computed for 4 years so
finally the answer is
$250 is invested at 8% annual interest compounded monthly for 4 years
hope this helps