Graph Exam 2 help

[baize888]

Can someone show me how to do this question like these step by step? Where they ask you the number of .... is at least two times the number of ...
3b)

[MightyBeh]

Can someone show me how to do this question like these step by step? Where they ask you the number of .... is at least two times the number of ...
3b)
(Image removed from quote.)

Just sub in the value they give you, like this

Since latex isn't working still, as far as I can tell, it might look a bit messy:
y =< (4/5) * 10, where we've subbed in the number of phones repaired.
y =< 8, simplified version of the above

So we can say that at most, 8 laptops can be repaired.