.
You "undo" what has been done to p.
The last thing done on the left is "multiply by 35" so the first thing you do to solve for p is divide both sides by 35:
Now, we have an exponential function (e to a power). The reverse of that is the "natural logarithm". Take the logarithm of both sides:
Finally, p is multiplied by -0.7. Divide both sides by -0.7: