in a
let's say the unmentioned angle is Y
so a line is 180° thus Y+145°=180°
we can get y=35°
so a triangle has inside angle sum of 180 and this gives us
X-25°+X+35°=180°
2X=170°
X=85°
for b
we know the inner angles of any four sided figure is 360°
X-35°+2X-75°+X+X=360°
5X=450°
thus X=90°
