You have a lot of questions here, I can help you with a few of them.
When you simplify the polynomials, you put together all of the terms that have the same degree. That means the variables have the same exponents. The number of terms are the items separated by plus and minus signs.
Here are the answers for the first three:
1)

2)

3)
Answer:
x=40
Step-by-step explanation:
4/25 = X/250
x=(4 . 250) /25
x=40
Answer:
0.99 cents each
Step-by-step explanation:
7.92 divided by 8= 0.99
Hope this helped
:)
Solve the following system:
{3 x - 5 y = 7 | (equation 1)
{10 y - 4 x = 16 | (equation 2)
Swap equation 1 with equation 2:
{-(4 x) + 10 y = 16 | (equation 1)
{3 x - 5 y = 7 | (equation 2)
Add 3/4 × (equation 1) to equation 2:
{-(4 x) + 10 y = 16 | (equation 1)
{0 x+(5 y)/2 = 19 | (equation 2)
Divide equation 1 by 2:
{-(2 x) + 5 y = 8 | (equation 1)
{0 x+(5 y)/2 = 19 | (equation 2)
Multiply equation 2 by 2:
{-(2 x) + 5 y = 8 | (equation 1)
{0 x+5 y = 38 | (equation 2)
Divide equation 2 by 5:
{-(2 x) + 5 y = 8 | (equation 1)
{0 x+y = 38/5 | (equation 2)
Subtract 5 × (equation 2) from equation 1:
{-(2 x)+0 y = -30 | (equation 1)
{0 x+y = 38/5 | (equation 2)
Divide equation 1 by -2:
{x+0 y = 15 | (equation 1)
{0 x+y = 38/5 | (equation 2)
Collect results:
Answer: {x = 15
{y = 38/5 or 7.6 decimal