If ∫13f(x)dx=7\int_1^3 f(x) dx = 7∫13f(x)dx=7 and ∫13g(x)dx=3\int_1^3 g(x) dx = 3∫13g(x)dx=3, what is ∫13(f(x)+2g(x))dx\int_1^3 (f(x) + 2g(x)) dx∫13(f(x)+2g(x))dx?
10
13
20
34