Two mechanics worked on a car. The first mechanic worked for 5 hours, and the second mechanic worked for 15 hours. Together they charged a total of $1550. What was the rate charged per hour by each mechanic if the sum of the two rates was $140 per hour?

The perimeter of a movie screen is 54 meters. the screen is 18 meters wide. how tall is it?

The avenues in a particular city run north to south and are numbered consecutively with 1st avenue at the western border of the city. the streets in the city run east to west and are numbered consecutively with 1st street at the southern border of the city. for a festival, the city is not allowing cars to park in a rectangular region bordered by 5th avenue to the west. 9th avenue to the east, 4th street to the south, and 6th street to the north. if x is the avenue number and yis the street number, which of the following systems describes the region in which cars are not allowed to park? 5th ave 9th ave

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).