Expand and simplify: 3 (g + 5) - 3 (g + 6)

3 (g + 5) - 3 (g + 6) =

3g + 15 - 3g - 18

The numbers before the parentheses are multiplied by numbers Inside parentheses

And:

3g - 3g - 18 + 15 = - 3

3g - 3g are symmetrical and destroy each other

- 3

distribute each bracket, multiplying the terms in the bracket by the value outside the bracket.

= 3g + 15 - 3g - 18 → (collect like terms)

= (3g - 3g) + (15 - 18) = 0 + ( - 3) = - 3