Question

If 3a +5b =10 and 5a +3b =30 what is the average of a and b?

Answer 1

Hello, please consider the following.

$3a+5b + 5a + 3b = 8(a+b)=10+30=40\\\\a+b=\dfrac{40}{8}=5$

And the average is

$\dfrac{a+b}{2}\boxed{=\dfrac{5}{2}}$

Thank you.