Give the digits 0-9, how many 4 digit numbers can be made if digits can be used more than once

If you roll two fair dice (one black die and one white die), in how many ways can you obtain a 4 on at least one die?

Aregular hexagon rotates counterclockwise about its center. it turns through angles greater than 0° and less than or equal to 360°. at how many different angles will the hexagon map onto itself?

The graph of f(x), shown below, resembles the graph of g(x) = x2, but it has been changed somewhat. which of the following could be the equation of f(x)?