t = 2/3. Multiply the numbers in the parentheses by -1. It becomes 9t + -3t + -3 = 1. Combine like terms to get 6t + -3 = 1. Add 3 to both sides to get 6t = 4. Divide both sides by 6. t = 2/3
Associative Property states that grouping symbols does not affect the outcome. This property works for Addition and Multiplication:
2 + (3 + 4) = (2 + 3) + 4
6 • (5 • 4) = (6 • 5) • 4