5n + 4
The number 5 is the numerical coefficient of n is the variable and 4 is constant.
-7x + 12
The number -7 is the numerical coefficient of the variable x. Note that negative sign on 7 is the part of the coefficient. The term 12 is a constant.
p + 3
The variable p is assumed to have a numerical coefficient of 1. The term 3 is a constant.
Sorry if this is all i got coz it is much simpler if its okay include also the numerical coefficient.
Hope this would help you... ^__^