To add or subtract terms with exponents, both the base and the exponent must be the same. In this case they are so subtract the coefficients and retain the base and exponent:

-9y⁴ - 9y⁴
(-9 - 9)y⁴
-18y⁴

To multiply terms with exponents, the base of both exponents must be the same. In this case they are so multiply the coefficients and add the exponents:

7z⁷ x 8z²
(7 x 8)z^{(7 + 2)}
56z⁹

If 59% of the town's 21,000 voters cast ballots the number of votes cast is:

(\( \frac{59}{100} \)) x 21,000 = \( \frac{1,239,000}{100} \) = 12,390

The mayor got 78% of the votes cast which is:

(\( \frac{78}{100} \)) x 12,390 = \( \frac{966,420}{100} \) = 9,664 votes.

To subtract these radicals together their radicands must be the same:

9\( \sqrt{28} \) - 8\( \sqrt{7} \)
9\( \sqrt{4 \times 7} \) - 8\( \sqrt{7} \)
9\( \sqrt{2^2 \times 7} \) - 8\( \sqrt{7} \)
(9)(2)\( \sqrt{7} \) - 8\( \sqrt{7} \)
18\( \sqrt{7} \) - 8\( \sqrt{7} \)

Now that the radicands are identical, you can subtract them:

A number with an exponent (b^e) consists of a base (b) raised to a power (e). The exponent indicates the number of times that the base is multiplied by itself. A base with an exponent of 1 equals the base (b¹ = b) and a base with an exponent of 0 equals 1 ( (b⁰ = 1).