Mitch and Bill are the same age. When Mitch is 25 years old, he begins depositing $100 every month into a long-term savings plan. He consist

I do not actually see any question here   

I suppose you want to know how much they each have at age 75 years ?

i = (0.07/12)

Mitch

How much after 10 years

$${\mathtt{100}}{\mathtt{\,\times\,}}\left({\frac{\left({\left({\mathtt{1}}{\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{0.07}}}{{\mathtt{12}}}}\right)\right)}^{\left({\mathtt{120}}\right)}{\mathtt{\,-\,}}{\mathtt{1}}\right)}{\left({\frac{{\mathtt{0.07}}}{{\mathtt{12}}}}\right)}}\right) = {\mathtt{17\,308.480\: \!743\: \!353\: \!610\: \!059\: \!6}}$$

After a further 40 years

$${\mathtt{17\,308.48}}{\mathtt{\,\times\,}}{\left({\mathtt{1}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{0.07}}}{{\mathtt{12}}}}\right)}^{{\mathtt{480}}} = {\mathtt{282\,325.739\: \!551\: \!243\: \!036\: \!749\: \!5}}$$

So it seems that Mitch will have    $282326

What about Bill

$${\frac{{\mathtt{100}}{\mathtt{\,\times\,}}\left({\left({\mathtt{1}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{0.07}}}{{\mathtt{12}}}}\right)}^{{\mathtt{480}}}{\mathtt{\,-\,}}{\mathtt{1}}\right)}{\left({\frac{{\mathtt{0.07}}}{{\mathtt{12}}}}\right)}} = {\mathtt{262\,481.339\: \!833\: \!333\: \!259\: \!683\: \!2}}$$

Bill will only have $262 481

So Mitch will have more at age 75 years