Expand the brackets: (3a+3)(a+4)

To expand this, we must multiply each term in both brackets separately and then add all of these terms together. First, multiply the first term in each of the brackets: 3a x a = 3a^2. Next multiply the first term in the first bracket by the second term in the second brackets: 3a x 4 = 12a. Next multiply the second term in the first brackets by the first term in the second: a x 4 = 4a. Lastly, multiply the second term in each of the brackets: 3 x 4 = 12. Now add these all up to get: 3a^2 + 12a + 4a + 12 = 3a^2 + 16a + 12