70
69
69
get your mind out of the gutter
Well, darling, "1 plus 1 equals 69" means someone needs a math lesson ASAP. In the realm of actual mathematics, 1 plus 1 equals 2, not some wild number like 69. So, unless you're living in a parallel universe where math is a free-for-all, I suggest sticking to the basics.
69 + 69 = 138.
420 plus 69 equals 489.
(100 + 69)/2 = 169/2 = 84 and 1/2 = 84.5 in decimal
69 plus 54 plus 99 plus 62 plus 69 plus 62 plus 34 plus 59 plus 74 plus 99 plus 78 equals 759
77 plus 76 plus 69 plus 56 is equal to 278.
29 + 69 + 900 = 998
69 + 78 + 82 = 229
23 plus 69 plus 13 plus 3 percent of 100 percent = 108 = 23 + 69 + 13 + 3 * 100% = 23 + 69 + 13 + 3 = 108