Step-by-step explanation:
28m+4n-12m+3
28m-12m+4n+3
16m+4n+3
Answer:

or -6.122
Step-by-step explanation:
In answering this kind of questions, you must take note of BODMAS. that is;
B - Bracket
O - Of (multiplication)
D - Division
M - Multiplication
A - Addition
S - Subtraction
and you have to answer by the order above to get the correct answer. thank you
hope it helps .