Add $1_3 + 12_3 + 212_3 + 2121_3.$ Express your answer in base 3.
Converting to base 10, we get 1 + 4 + 23 + 50. This is 79.
Converting back to base 3, 79 = 2221_3.
13=1123=1∗3+2=52123=2∗9+1∗3+2=2321213=2∗27+1∗9+2∗3+1=70
