a) \(\left(10-x\right)⋮\left(x-3\right)\Leftrightarrow\left[7+\left(3-x\right)\right]⋮\left(x-3\right)\Leftrightarrow7⋮\left(x-3\right)\)
\(\Leftrightarrow x-3\inƯ\left(7\right)=\left\{-7,-1,1,7\right\}\Leftrightarrow x\in\left\{-4,2,4,10\right\}\).
b) \(\left(x+5\right)⋮\left(x+2\right)\Leftrightarrow\left[\left(x+2\right)+3\right]⋮\left(x+2\right)\Leftrightarrow3⋮\left(x+2\right)\)
\(\Leftrightarrow x+2\inƯ\left(3\right)=\left\{-3,-1,1,3\right\}\Leftrightarrow x\in\left\{-5,-3,-1,1\right\}\).