If $a\equiv 16\pmod{37}$ and $b\equiv 21\pmod{37}$, then for what integer $n$ in the set $\{0,1,2,\ldots,35,36\}$ is it true that $$a-b\equiv n\pmod{37}~?$$
Question:
If $a\equiv 16\pmod{37}$ and $b\equiv 21\pmod{37}$, then for what integer $n$ in the set $\{0,1,2,\ldots,35,36\}$ is it true that $$a-b\equiv n\pmod{37}~?$$
Answer:
Let's think step by step.

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If $a\equiv 16\pmod{37}$ and $b\equiv 21\pmod{37}$, then for what integer $n$ in the set $\{0,1,2,\ldots,35,36\}$ is it true that $$a-b\equiv n\pmod{37}~?$$
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