In the expression * + 3 what is the coefficient of * ?

3 is the coefficient because it is the only number in the eqaution

A coefficient of a term is the number of times a variable appears, or in simple terms, the number next to the variable. In this case, "x" is your variable, and since there is no number next to "x", you can infer that there is only 1 x. Therefore, your coefficient of x in this particular problem would be 1.