Multiply first, then add. 12 times 7 = 84. Then add 8. 84 + 8 = 92.
In order to figure out what N is you have to isolate it by dividing by 50 on both sides as shown below:
4*d^(-3)*d^18 = 4*d^(18-3) = 4*d^(15). The trick here is to combine the exponents.
Another way to write this problem would be:
4*d^18
---------- . Here d^18 divided by d^3 results in d^15, so again the final
d^3 answer is 4*d^15.
