Add 35+ 72.5=107.5 that should give you your answer for c and the answer for d is acute because the triangle would have to be 360 to be Obtused and it's not a right triangle because you don't have a 90 degree angle
3951 is an example of a standard form.
What standard form means is the number is written in numerical form.
More examples: 5269, 95862, 125634, etc.
Answer:

Step-by-step explanation:
we know that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form
or 
Let
c ----> the total cost of the boat rental
d ---> is the number of days, the family rents the boat
we know that
Kaya's family spends $105 to rent a boat for 7 days
so
For d=7 days, c=$105
Find the value of the constant of proportionality k

substitute the given values

therefore
The linear direct equation is equal to

There will be 130 nickels and 90 dimes. 100 nickels is 5 dollars. 90 dimes are 9 dollars. And then there will be 30 left. 30 dimes isn’t 1.50$ bur 30 nickels is 1.50$ so you add the 30 to the nickels and it’ll be exactly 15.50$.
There is no sum for this geometric series. it diverges rather than converges due to the absolute value of the common ratio (r), which is -3, being 3. for a geometric series to have a sum (to converge), the absolute value of r must be less than 1.
(you find r by dividing a2/a1, a3/a2, etc.)
hope this helps