The sum of something is the result of addition so you know that they are adding p and 45 together. They then state that p plus 45 must be less than 89. You can show that by using the less than symbol "<"
If you want to find all of the different values that P could equal then all you have to do is subtract 45 from both sides so the equation would be
p < 44
this means that p can equal anything less than 44 for this statement to be valid. Hope this helped!
