Please help me with this I don't understand it. Please show your work also so I can understand better.

What is the vertex form of f(x) = x2 + 6x + 3

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?

In the diagram, gef and hef are congruent. what is the value of x