Hello! I believe your answer is r = 8.
Here's how I got it :
42 - 5r = 2
42-42 - 5r = 2-42 , we subtract 42 to move it over to the right to isolate the 5r. And now we evaluate it!
-5r = -40
-5r/-5 = -40/-5 divide by -5 to isolate the r
that leaves us with : r = 8