how is this a tst problem (a) note that all of these must have every number that isn't the middle number equal, and thus our answer is $9\cdot10=\boxed{90}$ wow what an impossible tst problem (b) omg this is so so so much harder!1!!!!1!11!111! anyways we do casework on if there are exactly $2021$ equal digits or not: more than 2021: This is $90,$ see (a). exactly 2021: more casework the first digit is one of the 2021: There are $1010$ ways to pick the number that isn't equal, $10$ ways to pick what this number is, $9$ ways to pick the equal digit, $90900$ total ways. the first digit isn't one of the 2021: There are $9$ ways to pick the first digit and $10$ ways to pick all other digits, $90$ total ways. In total, there are $90900+90+90=\boxed{91080}$ watch me get this wrong