Astudent has a savings account with d dollars in it. the student plans to withdraw w dollars each month for n months

Lets assume that b is how much money the student has in their bank account.

So, the equation for that question would be b = d - wn.  

because the two particles have an equal charge, the charges will cancel out and give the atom an overall charge of 0. so, if at atom has 35 protons in the nucleus, we could expect it to have 35 electrons orbiting that nucleus.

it's actually d for edge-nuity.