Robert, Brenna, and Christian got different answers for this problem: (-40)-2[(-8)÷2] Robert's answer was -32, Christian's answer was -48, and Brenna's is 168. Which student had the correct answer?
Explain how the other two got their answers. What errors did they make?

Abox contains 1 plain pencil and 4 pens. a second box contains 5 color pencils and 5 crayons. one item from each box is chosen at random. what is the probability that a plain pencil from the first box and a color pencil from the second box are selected? write your answer as a fraction in simplest form.

Lisa has three classes that each last 50 minutes. what is the total number of minutes of the three classes

Asquare and an equilateral triangle have the same perimeter. each side the triangle is 4 inches longer than each side of the square. what is the perimeter of the square