(this is multiple choice and i raised points make sure to EXPLAIN !)

whats the sum of f and g ?
f(x)=10-2x and g(x)=7x+5

a) (f+g)(x)=5+5x
b) (f+g)(x)=5+9x
c) (f+g)(x)=15+5x
d) (f+g)(x)=15+9x