Answer:
9 hr
Step-by-step explanation:
vary directly means you should think about a constant being multiply to one variable to get another variable.
So we have E=kH
where E=earnings and H=hours and k is the constant of proportionality
So they give us when H=7 we have E=77 giving us 77=k(7) which means the constant of proportionality is 11
So that means no matter what the E and H are k is 11
So we have the equation is E=11H
Replace E with 99 and solve for H
99=11(H)
So H=9
9 hours
