Question

(9x-12)-(5x-7) please explain it to me​

Answer 1

Use the foil method
FIRST
OUTER
INNER
LAST
9x by 5x
9x by -7
-12 by 5x
-7 by -12
Then add and subtract like terms to get the answer.

Answer 2

Simplifying
(9x + -12) + -1(5x + -7) = 0

Reorder the terms:
(-12 + 9x) + -1(5x + -7) = 0

Remove parenthesis around (-12 + 9x)
-12 + 9x + -1(5x + -7) = 0

Reorder the terms:
-12 + 9x + -1(-7 + 5x) = 0
-12 + 9x + (-7 * -1 + 5x * -1) = 0
-12 + 9x + (7 + -5x) = 0

Reorder the terms:
-12 + 7 + 9x + -5x = 0

Combine like terms: -12 + 7 = -5
-5 + 9x + -5x = 0

Combine like terms: 9x + -5x = 4x
-5 + 4x = 0

Solving
-5 + 4x = 0

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '5' to each side of the equation.
-5 + 5 + 4x = 0 + 5

Combine like terms: -5 + 5 = 0
0 + 4x = 0 + 5
4x = 0 + 5

Combine like terms: 0 + 5 = 5
4x = 5

Divide each side by '4'.
x = 1.25

Simplifying
x = 1.25