Jj sell tablets at a store. He earns $180 a week plus$15 for ever tablet he sells. Jj earns $315 last week. Write a equation that can be used to determine the number of computers Jj sold last week. how many was sold

so Jj earns a flat rate of 180 per week and an extra 15 per tablet he has sold
so what we need to do is subtract his flat rate(180) from his total(315)
 315
-180
____
135 So now we know how much money Jj has earned from selling tablets. But we still need to create an equation and find out how many he has sold.
So we know he get $15 per tablet so 135÷15=9
now we know he has sold 9 tablets
Bu what is our Equation?
well, what were the steps?
TP = total pay
FR= Flat rate
C= Computer profit
PPC= price per computer
#C = number of computers

#C = TP-FR=C C÷PPC=#C
can we simplify this further?
#C = C÷PPC
lets do this:
#C= x
C= y
PPC= z 
So:              (X = Y÷Z)