i can not figure it out im always getting wrong answer

i can not figure it out im always getting wrong answer

A hall charges $30 per person for a sports banquet when 200 people attend. For every 10 extra people that attend, the hall will decrease the price by $1 per person. What number of people will maximize...

Pi=3.14 V=8.800cm3 h=28cm r=??

factorise each of the following expressions completely a) 6x^2y^2-5xy-4 b) 3z-8xyz+4x^2y^2z c) 36y^2-49(x+1)^2

-X2+2x+2=

Please help me solve the equation with the folowing method: x2+12x-64=0 1. Move the constant term to the right side of the equation. 2. Multiply each term...