4(3m - 4)
m(12 + 7n)
18m-7+12m
Not unless m = n.
An algebraic expression
-6
If you mean: 12(3+m) then it is the same as 36+12m
12(m+n)
30m-7
Assuming you mean 12m + 12n, you can use the distributive property to take out the common factor 12.
(m - 2)(m - 10)
(3+2) (4+48)
1m = 100cm, therefore 12m = 1200cm. 12m is > 120 cm