Differentiate Cos25º - Sin 25º

The mean of the numbers 13, 16, x, 18, 21, 2x, 35, is 22. Find the value of x

Find the variance of a group of data whose standard deviation is 12.34 to the nearest whole number.

Calculate the standard deviation of the following scores 5, 4, 6, 7, and 8

From a class of 5 girls and 7 boys, a committee consisting of 2 girls and 3 boys is to be formed. How many ways can this be done?