Explanation

We can use the formula for the difference of squares:

a² - b² = (a - b)(a + b)

Here a = 21, b = 19

21² - 19² = (21 - 19)(21 + 19)

= (2)(40) = 80

Explanation

It looks like there’s a small mistake in the equation format.

Assuming the intended equation is:

x−5=10

Let's solve for x:

1; Add 5 to both sides to isolate 

x=10+5=15

Explanation

a^4 x a^8 x a^3 =?

a^4 has an exponent of 4.

a^8 has an exponent of 8.

a^3 has an exponent of 3.

Add the exponents together: 4 + 8 + 3 = 15.

Therefore, a^4 x a^8 x a^3 simplifies to a^15.

Explanation

4 - 3x = 8 - x

Solve step-by-step:

1. Move all x terms to one side:

   4 - 3x + x = 8  

   ⇒ 4 - 2x = 8

2. Subtract 4 from both sides:

   -2x = 4

3. Divide by -2:

   x = -2

Explanation

3x - 15 - 6 = 0

3x = 21

X = 21/3

X = 7