Question

-15=-4m+58n+7=31-10=10(k-9)

Answer 1

$-15=-4m+5\ \ \ |both\ sides\ /+4m\\\\4m-15=5\ \ \ \ |both\ sides\ /+15\\\\4m=20\ \ \ \ |both\ sides\ /:4\\\\\underline{\underline{m=5}}$

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$8n+7=31\ \ \ \ |both\ sides\ /-7\\\\8n=24\ \ \ \ |both\ sides\ /:8\\\\\underline{\underline{n=3}}$

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$10(k-9)=-10\ \ \ \ |both\ sides\ /:10\\\\k-9=-1\ \ \ \ |both\ sides\ /+9\\\\\underline{\underline{k=8}}$

Answer 2

$1)\ \ \ -15=-4m+5\\-15-5=-4m\\-20=-4m\ /:(-4)\\5=m\\m=5\\\\2)\ \ \ 8n+7=31\\8n=31-7\\8n=24\ /:8\\n=3\\\\3)\ \ \ -10=10(k-9)\ /:10\\-1=k-9\\-1+9=k\\8=k\\k=8$