To solve this equatio you use the next property:
Subtraction Equal Property: it is used in expressions with adds. State that you can substract the same amount from both sides of the equation and maintain euality.
In this case, to solve r you substract 18 in both sides of the equation:
[tex]r+18-18=26-18[/tex]As 18-18 is 0;
[tex]r=8[/tex]Then, The solution of r+18=26 is r=8