OK, let's work through this together. We're starting with 991 and we're going to multiply it by 16, which means we add 991 to itself 16 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

So, 991*16 = 15856