I need help on this. (the middle one)

What are the soultion(s) to the quadratic equation 40- x^2=0

Ametal rod is 2/5 meters long. it will be cut into pieces that are each 1/30 meters long. how many pieces will be made from the rod?

Ineed big ! the cost of a school banquet is $25 plus $15 for each person attending. create a table, sketch the graph, and write an equation in slope-intercept and point-slope form that gives total cost as a function of the number of people attending. what is the cost for 77 people?