Hi!
So, we need to figure out what r equals.
r doesn't have to be a number. r has to equal a value. A value can be variables, or numbers, it doesn't matter.
The equation says r = t + m. Read the equation out loud.
r equals t plus m.
There's the value of r!
The answer is the problem: r = t + m
Hope this helps! :)
-Peredhel