Answer: 10xy-12+15x-8y=(5x-4)*(2y+3).
Step-by-step explanation:

9/20
explanation:
7/10 - 1/4
14/20 - 5/20
14-5/20
9/20
Answer:
240 students
Step-by-step explanation:
Grade 7 : Grade 8 = 5 : 3
Number of seventh grade students = 5x
Number of Eighth grade students = 3x
3x = 90
x = 90÷3
x = 30
Total students = 5x + 3x = 8x = 8 * 30 = 240
Answer:
36.58% probability that one of the devices fail
Step-by-step explanation:
For each device, there are only two possible outcomes. Either it fails, or it does not fail. The probability of a device failling is independent of other devices. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

In which
is the number of different combinations of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.
A total of 15 devices will be used.
This means that 
Assume that each device has a probability of 0.05 of failure during the course of the monitoring period.
This means that 
What is the probability that one of the devices fail?
This is 


36.58% probability that one of the devices fail