Question 404792
The most important thing to remember here is PEMDAS. Its the order of equations acronym.

PEMDAS
P: parentheses 
E: exponents
M: multiplication
D: division
A: addition
S: subtraction

If you start solving the equation in that order, you'll be fine. Here's how you do it. 

m+3(m-4)=16
Now you distribute the 3 throughout the parentheses(P). Multiply both things inside the parentheses by the number on the outside.
m+(3m-12)=16
You don't need the parentheses anymore since you've finished distributing.
m+3m-12=16
Since you have two "m" variables in your equation, you can combine them. Just add them together. 
4m-12=16
You can now add that "-12" to the other side. You want to isolate the variable, the letter, on one side, so you can solve for it. 
4m-12=16
      +12  +12
4m=28
Now you divide both sides by the number next to the variable, to get rid of it. 
4m=28
÷4  ÷4
And there's your answer.
m=7