The complete table will be:

<u><em>Explanation</em></u>
Suppose, the number of sit-ups in Sunday is 
Mean is the simple average of some numbers. <u>For finding the mean number</u> of sit-ups per day, we need to <u>divide the 'total number of sit-ups' by the 'total number of days'</u>.
Here the total number of days is 7 and the total number of sit-ups for 7 days 
Given that, the mean number of sit-ups per day is 100. So, the equation will be...

So, the number of sit-ups you have to do Sunday is 175.
Answer:
Multiply the first equation by 4.
Step-by-step explanation:
4(x+y=3) which gives
4x+4y=12
and
4x-y=7
Then subtract the two equations and the x variable will be eliminated.
If you want me to solve for "Y" then, the answer will be,

ir if you want me to solve for "X" instead then the answer will be,

Answer:
The change in value is 19,000 altogether and 1900/year
Step-by-step explanation:
Change in value:
initial value - final value
= $26,000 - $7000
= $19,000
Change in value/year:
change in value/time
= $19,000/10
= $1900/year