In which case would it be most appropriate to use km as a unit of measurement a: length of a cat b: width of a human hair c: circumference of the earth d: diameter of a quarter pls answer asap like answer today pls anyone that answers make sure its right you.

The sum of the product of 4 and x and the product of 7 and y is 61. the sum of the product of 12 and x and the product of 21 and y is 61. what are the values of x and y?

These question are hard can you me with answers

The chs baseball team was on the field and the batter popped the ball up. the equation b(t)=80t-16•16+3.5 represents the height of the ball above the ground in feet as a function of time in seconds. how long will the catcher have to get in position to catch the ball before it hits the ground? round to the nearest second