7 - 2k, maybe im not sure it's been a while since ive done that, but k is the variable then "a number" should be K
3m²n + 12mn²
3mn(m) + 3mn(4n)
3mn(m + 4n)
The GCF of this expression is 3mn.
4 for the first one and 1.5 for the second one
I found this for you. It even tells you how the answer was achieved.
