Respuesta :

Hello, please consider the following.

[tex]3a+5b + 5a + 3b = 8(a+b)=10+30=40\\\\a+b=\dfrac{40}{8}=5[/tex]

And the average is

[tex]\dfrac{a+b}{2}\boxed{=\dfrac{5}{2}}[/tex]

Thank you.