The answer is to call me quick
that differences are that mass is a measurement of the amount of matter something contains and mass is measured by using a balance comparing a known amount of matter to an unknow of matter
You have to combine like terms, so the variable (x, y, s, d, c....) and the exponents must be the same in order to combine them.
For example:
x² + x³ Since they don't have the same exponent, you can't combine them
y² + 3y² = 4y²
23x + x = 24x
4. 2s² + 1 + s² - 2s + 1 You can rearrange it if it makes it easier
2s² + s² - 2s + 1 + 1 = 3s² - 2s + 2
5. 5t² - 2t - 1 - (3t² - 5t + 7) Distribute/multiply the - to (3t² - 5t + 7)
5t² - 2t - 1 - 3t² + 5t - 7 = 2t² + 3t - 8
Do the same for #9 and #10, and you should get:
9. 2k² + 5k - 9
10. 6y³ - 7y² - 6y - 12
72°
the sum of the exterior angles of a polygon = 360°
for a pentagon with 5 sides the
exterior angle = 
= 72°
