Elimination Method

If we multiply the equation 3 by (-1) we obtain this:

If we add them we obtain 0, therefore there are infinite solutions. So, let's write it in terms of Z
1. Using the 3rd equation we can obtain X(Y,Z)

2. We can replace this value of X in the 1st and 2nd equations

3. If we simplify:

4. We can obtain Y from this two equations:

5. Now, we need to obtain X(Z). We can replace Y in X(Y,Z)

6. If we simplify, we obtain:

7. In conclusion, we obtain that
(X,Y,Z) =
129 rounded to the nearest ten is 130.
When you round to the nearest ten, you should be looking for;
10, 20, 30, 40, 50, 60, 70, 80, 90.
Answer:
35 is a reasonable amount
Step-by-step explanation:
Since all of the books cost around $7 and there are 5 books
when you multiply 7x5=35