An experiment consists of randomly drawing one marble from a bag containing 7 purple, 4 blue, and 3 green marbles. what is the probability of selecting a purple marble from the bag if the answer is expressed as a fraction?

Write numerical coefficient of y² in the expression 2x² - 15xy – 7y²

Expresa commuter train leaves downtown sation and travels at a average speed of 55 miles per hour towards the north side sation, which is 50miles away. thirty minutes later, express commuter train #7 leaves north side and travels at a average speed of 35miles per hour towards downtown sation. at the moment the two trains pass each other, how far(in miles) is train #12 from the downtown sation and how long(in minutes) has the #12 train been traveling

Aswimming pool had 2.5 million liters of water in it. some water evaporated, and then the pool only had 22 million liters of water in it. what percent of the water evaporated?