Find the value of each variable

Find the solution of system of equation y= x-4 y=4x+2

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?

Given the median qr and trapezoid mnpo what is the value of x?