Two mechanics worked on a car. The first mechanic charged $115 per hour, and the second mechanic charged $50 per hour. The mechanics worked for a combined total of 25 hours, and together they charged a total of $2,550. How long did each mechanic work?

Using elimination, what is -4x+2y=-12 4x+8y=-24

Amachine that produces a special type of transistor (a component of computers) has a 2% defective rate. the production is considered a random process where each transistor is independent of the others. (a) what is the probability that the 10th transistor produced is the first with a defect? (b) what is the probability that the machine produces no defective transistors in a batch of 100? (c) on average, how many transistors would you expect to be produced before the first with a defect? what is the standard deviation? (d) another machine that also produces transistors has a 5% defective rate where each transistor is produced independent of the others. on average how many transistors would you expect to be produced with this machine before the first with a defect? what is the standard deviation? (e) based on your answers to parts (c) and (d), how does increasing the probability of an event a↵ect the mean and standard deviation of the wait time until success?

Me d is also an option but i couldn't get it in the picture