part a:
this is really just intuition. you can go either way as long as you back up what you say.
either you think hunter would be faster because he starts out with a lot more money, or you think amado would be faster because he earns a lot more.
part b:
let x be the number of hours hunter works, and y the number that amado works.
they both need to earn 600 dollars.
hunter's money is modelled by 150 + 7.5x
to get 600 dollars
150 + 7.5x = 600
7.5x = 450
x = 60
amado's money is modelled by 12y
to get 600 dollars
12y = 600
y = 50
hunter would need to work 60 hours to make enough money, but amado would only need to work 50, so hunter will take longer.
then say whether this agrees with what you guessed in part a