If a quadrilateral has three angles measuring 60',45' and 100' what is the angle of the fourth angle

What term makes it inconsistent y=2x - 4 ?

The median of a data set is the measure of center that is found by adding the data values and dividing the total by the number of data values that is the value that occurs with the greatest frequency that is the value midway between the maximum and minimum values in the original data set that is the middle value when the original data values are arranged in order of increasing (or decreasing) magnitude

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15