OK, let's work through this together. We're starting with 991 and we're going to multiply it by 29, which means we add 991 to itself 29 times.
Step 1: 0 + 991 = 991
Step 2: 991 + 991 = 1982
Step 3: 1982 + 991 = 2973
Step 4: 2973 + 991 = 3964
Step 5: 3964 + 991 = 4955
Step 6: 4955 + 991 = 5946
Step 7: 5946 + 991 = 6937
Step 8: 6937 + 991 = 7928
Step 9: 7928 + 991 = 8919
Step 10: 8919 + 991 = 9910
Step 11: 9910 + 991 = 10901
Step 12: 10901 + 991 = 11892
Step 13: 11892 + 991 = 12883
Step 14: 12883 + 991 = 13874
Step 15: 13874 + 991 = 14865
Step 16: 14865 + 991 = 15856
Step 17: 15856 + 991 = 16847
Step 18: 16847 + 991 = 17838
Step 19: 17838 + 991 = 18829
Step 20: 18829 + 991 = 19820
Step 21: 19820 + 991 = 20811
Step 22: 20811 + 991 = 21802
Step 23: 21802 + 991 = 22793
Step 24: 22793 + 991 = 23784
Step 25: 23784 + 991 = 24775
Step 26: 24775 + 991 = 25766
Step 27: 25766 + 991 = 26757
Step 28: 26757 + 991 = 27748
Step 29: 27748 + 991 = 28739

So, 991*29 = 28739