How do you simplify the expression #8+(9t+4)#?
There's really not much you can do to this expression, other than adding like terms and factoring.
Notice that the paranthesis in not multipies by another term, which means that you can write the expression as
#8 + (9t + 4) = 8 + 9t + 4#
Now you acn group like-terms and add them to get
#9t + 8 + 4 = 9t + 12#
You can factor this expression by
#9t + 12 = 3 * 3t + 3 * 4 = color(green)(3 * (3t+4))#