[Guntitat Gun]

2. ${\frac{\sqrt54}{\sqrt2}-\frac{4}{\sqrt8}+\frac{12\sqrt3}{\sqrt6}-\frac{18}{\sqrt3}}$
${=3\sqrt{3}-\sqrt{2}+6\sqrt{2}-6\sqrt{3}}$
${=5\sqrt{2}-3\sqrt{3}=a\sqrt{2}+b\sqrt{3}}$
จะได้ ${a=5,b=-3}$
ดังนั้น ${2a+b=2(5)+(-3)=7}$

ตอบ 7