In the first figure we have an angle that subtends a diameter. Those are always right angles, so
Answer: x=90 degrees
In the second figure we have to notice that the measure of arcs and central angles are interchangeable -- the measure of an arc is its central angle.
The units are implicitly degrees; the 10 should say 10°
These are supplementary angles so they add to 180°
3x + (7x + 10) = 180
10x = 170
x = 17
Answer: x=17
17° would be more accurate but the units are a bit ambiguous here so I'll leave it.