The decimals in front of the parentheses can be distributed to the number inside giving us: .3r-.6=.2r-.4
Then we combine like terms, and it doesn't matter what side you move what to: .1r=2
Now that we have reached this point we divide both sides with the number in front of 'r': .1r/.1=2/.1
After you do that, we have our answer: r=20
Hope this helped you out! :)
