Answer:
12x +7
Explanation:
First determine what numbers are coefficients. Because 3 and 4 don't have a variable in them, we know they are coefficients. You can then add them together to get 7. After that, we see that 5x and 7x both share the variable x. Because they share the same variable you can add them together to get 12x. Because 12x and 7 don't have the same variable you cannot add them together. This means that 12x + 7 is your final answer.