Distributing a Subtraction

Multiply every term inside the bracket by the number outside, and keep the sign of each term. So 3(x - 4) = 3x - 12, because 3 * (-4) = -12. If you write 3x - 4, the second term has not been multiplied. To solve 3(x - 4) = 9, expand the bracket, add 12 to both sides, then divide by 3:

3(x - 4) = 9

3x - 12 = 9

3x = 21

x = 7

A negative number outside a bracket changes every sign inside: -2(x - 5) = -2x + 10. Read the outside number with its sign, and multiply each term inside by it. Check the answer above: 3(7 - 4) = 3 × 3 = 9.