-9(4+x)>-126
-36-9x>-126
-36+36-9x>-126+36
-9x>-90
-9x/-9<-90/-9
x<10
I'll do a similar problem, and I challenge you to do this using similar techniques!
If John works for 15$ a hour with his friends rather than working for 20$ an hour for 50 hours a month, what's the monthly opportunity cost?
John would make 20*50=1000 dollars a month at the second option as he makes 20$ an hour 50 times. Next, if he works with his friends, he makes 15*50=750 dollars as he works 50 hours for 15 dollars an hour, or adds 15 50 times.
His opportunity cost would be <highest money>-<lowest money>=1000-750=250 dollars a month. Good luck on this question, and feel free to ask further questions!
