Mean = average; so (77+10)/2 = 43.5 = mean of 77 plus 10.
10 + 77 = 87
12 + 65 = 77 (this is in base 10, of course).
154
50 + 10 + 10 + 5 + 1 + 1 = 77
77 plus 76 plus 69 plus 56 is equal to 278.
77 over 10 = 77/10
77 + 89 = 166
77 + 1234 = 1,311
77 + 84 = 161
76+77=153
84 + 96 + 72 + 77 + 91 = 420
51 percent plus 77 percent = 128 percent 51% + 77% = 128%