[tex]f(x)=3^x+10x,\ g(x)=5x-3\\\\(f-g)(x)=f(x)-g(x)=(3^x+10x)-(5x-3)\\\\=3^x+10x-5x+3=3^x+5x+3[/tex]
[tex]Answer:\ \boxed{B.\ 3^x+5x+3}[/tex]
