The measure of a quadrilateral's angles always add up to 360º.
The three angles already given here are 70º, 25º, and 50º. Those together are:
70 + 25 + 50 = 145 Subtract this from 360 to find out how many degrees are left to be x.
360 - 145 = 215
The last angle must be 215º. x = 215
Hope this helps!