well, let's first convert it to a fraction... notice 2.85 has two decimals, so we'll use 2 zeros at the bottom, with a 1, and lose the dot.
[tex]\bf 2.\underline{85}\implies \cfrac{285}{1\underline{00}}\implies \cfrac{57}{20}
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\textit{20 goes into 57 twice, with a \underline{remainder} of 17}\qquad 2\frac{17}{20}[/tex]
