What's the problem? There's no example...
Try plugging in 4,6, and -7 into the x's
During 7 hours: 28 parts assembled
during 14 hours: 56 parts assembled
during 21 hours: 84 parts assembled
during 28 hours: 112 parts assembled
during 35 hours: 140 parts assembled
Your answer is c, common sense
Each girl will get 4 tangerines