The answer is 92.
Let’s see what multiples of 10 add up to 80:
10+10+60, 10+20+50, 10+30+40, 20+20+40, 20+30+30.
Imagine the numbers had all been rounded up:
9+9+59=77, which is less than 80.
But if each number is rounded down to the nearest 10 the maximum ones digit is 4 for each of them, and 3 times 4 is 12, added to 80 is 92:
14+14+64=
14+24+54=
14+34+44=
24+24+44=
24+34+34=92.