\(x+2y⋮5\)
\(\Rightarrow3x+6x⋮5\)
\(\Rightarrow3x+6y+10y=3x+16y\)
\(3x+6y+10y⋮5\)
Vậy 3x + 16y chia hết cho 5
\(x+2y\) chia hết cho 5
\(\Rightarrow3x+6y\) chia hết cho 5
\(\Rightarrow3x+6y+10y\) chia hết cho 5
\(\Rightarrow3x+16y\) chia hết cho 5 (đpcm)