Why you would make one of the addends a tens number when solving an additional problem

Answer question above and explain each step : )

Find the area of the regular hexagon if a side is 20 cm.

For problems 29 - 31 the graph of a quadratic function y=ax^2 + bx + c is shown. tell whether the discriminant of ax^2 + bx + c = 0 is positive, negative, or zero.