Find 3 multiple 1,789 how is multiplying a 3 digit number like multiplying a 4 digit number

Any is very appreciated! (picture is provided below)not sure how to do this at all won't lie

Weekly wages at a certain factory are normally distributed with a mean of $400 and a standard deviation of $50. find the probability that a worker selected at random makes between $450 and $500

Two line segments are shown in the figure below. suppose that the length of the line along the x-axis is 6, and the length of the hypotenuse of the triangle is 10. what is the equation of the hypotenuse line (shown in red, below)?