Answer:
3n+16
Step-by-step explanation:
three times: (3) a number n +16
(3)n+16 or 3xn+16
3n+16
The answer is, (1, -5)...
The equation (form) is: 
The solution of the equation is: 
Explanation:
First, let's call the number we are going to solve for "x".
Then two thirds of this number can be written as:

Then "plus 4" means add 4 we get:

"is 7" means that the above expression is equal to 7 (as follows):

The solution of the above equation is:

Ugh, these questions.
21x^3y^4 + 15x^2y^2 - 12xy^3
3xy^2 (7x^2y^2 + 5x - 4y)
Clearing up clutter...
3xy² (7x²y² + 5x - 4y)
That's your answer. Thanks for working my brain. ;)