Ok, so if you’re saying -18=r-3, then first you need to add 3 to each side so you can move the 3 with the -18 so you can isolate r. (Leave it by itself). So now your equation is -18+3=r. Next, combine like terms, so do -18+3, which is -15. Now you have -15=r, so r is equal to -15.
