Answer:

Step-by-step explanation:
By definition if two events are mutually exclusive then they are disjoint events, that is, they can not occur at the same time.
In general terms we say that events are mutually exclusive, then:

In this case we have that

But A and B are mutually exclusive events, then 
Answer:

And replacing we got:

And we can calculate this probabilit using the normal standard distribution or excel and we got:

Step-by-step explanation:
If we define the random variable of interest "the amount spent by a family of four of food per month" and we know the following parameter:

And we want to find the following probability:

And we can use the z score formula given by:

And replacing we got:

And we can calculate this probabilit using the normal standard distribution or excel and we got:

Simple Proof:
a) In the image, we know that ABCD is a parallelogram and that means opposite angel measures should be the same. We know that angel DCB is made up by angel 1 and 2, and angel DAB and DCB are equal and angel DAB is made up by angel 1 and <em>x</em>. So now we can conclude that angel <em>x</em> is equal to angel 2.
b) According to the definitions of a parallelogram, opposite angel measures have to be the same, while AECF have angle 1 to angel 1 and angel 2 to angel 1. We can conclude that AECF is <u>NOT</u> a parallelogram. (Sorry, you didn't give me the full question so some information remains unclear. )
If he need 380 to buy the bike but already has35, the he needs 380-35 = 345 more. if he makes 15 a week delivering papers, divide 345 by 15 to get the number of weeks it will take to save. 345/15=23 23 weeks