Answer:
1) 25+7(n-1)
When the above 'n'(hours) is substituted on the equation, it equals up to the right cost.
2) Given that n represents the no.of bikes, you just plug it in to the equation below.
250+39(n-1)
= 250+39(20-1)
= 250+39*19
= 250+741
= 991
30. Set up a proportion of 6/2 and x/10. cross multiply 6 times 10 and you get 60. divide 60 by 2=30
I hope this helps, i got it from a cheat sheet online

that is what you're solving and the answer, I turned 3/4 into 75% then divided
F = 30
g = 15
Yeah, hope this helps, etc.