Could somebody please help me with number 3 and number 4. thank y’all so much <3

Show algebraically that f and g are inverse functions f(x)=x^2/-6; g(x)=square root of 2x+12

Oscar and julie ashton are celebrating their 15th anniversary by having a reception hall. they have budgeted $4,500 for their reception. if the reception hall charges a $90 cleanup fee plus & 36 per person, find the greatest number of people that they may invite and still stay within their budget.

When 142 is added to a number the result is 64 more then 3 times the number. option 35 37 39 41