Verify the identity
cos ( x + pi/2) = -sin x

School has 204 sixth grade students. if the sixth grade is 30% of the total school, how many students are in the middle school?

Astore sells 4 apples for $3 and 3 oranges for $4 if pete buys 12 apples and 12 oranges how much will it cost

Azul has 4 green picks and no orange picks.you add orange picks so that there are 2 orange picks for every 1 green pick.how many picks are there now.