When changing an integral to polar coordinates, dxdy becomes rdrdtheta. can anyone give a satisfying explanation for where this r comes from?

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=

Steve had 48 chocolates but he decided to give 8 chocolats to each of his f coworkers. how many chocolates does steve have left

Damon makes 20 cups of lemonade by mixing lemon juice and water. the ratio of lemon juice to water is shown in the tape diagram. lemon juice\text{lemon juice} lemon juice water\text{water} water how much lemon juice did damon use in the lemonade? cups