<s>[INST] Solving $315 x \equiv 5 \pmod {11}$ I have to solve this: $$315 x \equiv 5 \pmod {11}$$
Isn't it like that?
$$315 \equiv (22+8) \cdot 10+15 \equiv 8 \cdot 3+4 \equiv 5+8+4 \equiv 6$$
Or have I done something wrong?
 [/INST] $315\equiv 7\pmod{11}\\7x\equiv5\pmod{11}\\-4x\equiv-6\pmod{11}\\2x\equiv3\pmod{11}\\2x\equiv-8\pmod{11}\\x\equiv-4\pmod{11}\\x\equiv7\pmod{11}$
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