Mark’s brother is five years older than Mark. Their combined ages add up to 23. How old is Mark?

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?

What is the area of the shaded sector?

An expression for the average of x 2x and 3y