Lets say that Maggie works 5 hours just the same as Braxton. if we use h(x)=f(x)+g(x) they would make about $100 combined. having to split that Braxton would make less then what he originally. since 9(5)+10= 55 and 6(5)+15=45. but if say Maggie works more then 5 hours then Braxton will be more money then just working alone.
Y = 2/7x - 4
y + 4 = 2/7x
4 = 2/7x - y (multiply everything by seven to get rid of the fraction)
28 = 2x - 7y
2x - 7y = 28
Your proof is correct and very well done
