number is 2.68
fraction is 0.68 = 68/100
mixed number is 2 68/100
cancel down 2 34/50
cancel down 2 17/25
-11/12 + 3/4 = -11/12 + 9/12 = (-11 + 9)/12 = -2/12 = -1/6
(1/2) of 24 chose A, so 12 chose A
of the remaining 12, (1/3) chose B, so 4 chose B
leaving 8 to choose C
t/15 = 1 2/5
t/15 = 7/5
t = 15 * 7/5
t = 3*7
t = 21
well I can only really help you with the last three question because I did this stuff along time ago and forgot most of it. For the second question you should rearrange the equation so that the negative turns into a minus, after that try getting a common denominator and then just subtract them.
For the 3rd one try multiplying the percentage of students by the total number of student to get the number of students that chose that song. After you get both, add them up and subtract that from the total number of students to acquire your answer.
For the last one, get the right side of the equation to just a numerator over a denominator and cross-multiply, after that it should be easier.
Hope that helps.
btw maverick, kids learn best if they try it for themselves instead of seeing the answer.