Question

find the value of x. (3x-4) (7x+4)

Answer 1

Answer:

$3x - 4 + 7x + 4 = 180 \\ 3x + 7x = 180 \\ 10x = 180 \\ \frac{10x}{10} = \frac{180}{10} \\ x = 18 \: \: degrees$

Answer 2

Answer:

x=18

Step-by-step explanation:

The 2 angles are on a straight line, and are therefore supplementary. This means that they add to 180 degrees.

So,

3x-4+7x+4=180

First, combine like terms

(3x+7x)+(-4+4)=180

10x+0=180

10x=180

Now, we need to solve for x. To do this, we must get x by itself. Since x and 10 are being multiplied, divide both sides by 10. We divide because division is the opposite of multiplication.

10x/10=180/10

The 10s on the left cancel, so we are left with:

x=180/10

x=18