First, use distributive property:
5(2r+6)-12r The original expression; multiply 5 by 2r, and 5 by 6.
10r+30-12r Keep the -12r, just add it on to the end of the number(s) you found
Next, use communitive property:
10r+30-12r What we found in the previous step
-2r+30 Combine the like terms; 10r-12r=-2r, then place the 30 at the end
Done! Your answer is -2r+30.
Hope that helps!